common.js + flow.js + index.html + flow.html: cookie scrub + doc pointers (#712 batch 13 cont.)

Final dashboard frontend cleanup. Four files at 0 cookies each.

common.js (11 → 0):
- #406 module-split history → drop, present-state intro
- #448 SharedWorker SSE pipe (×3) → docs/web-ui.md SSE multiplexing
  paragraph pointer
- #515 worker-death self-heal (×3) → docs pointer + brief inline
- #453 bfcache argus-nit (×2) → drop framing, keep inline why
- #451 drag-to-resize → docs/web-ui.md::Side panel pointer
- #233 marked autolinks new-tab → drop cookie

flow.js (8 → 0):
- #406 module-split history → drop
- #389 banner-in-footer → drop framing
- #375 stacking context → docs/web-ui.md::Per-agent page Terminal-wrap
- #408 server-side filter, #499 backend allow-list → drop cookies,
  keep inline why
- #448 SharedWorker per-URL keying → docs pointer
- #163 SSE catchup drift → drop cookie, keep inline why

index.html (13 → 0):
- #389 chrome history → drop
- #459 schedules, #607 matrix, #609 nginx-front, #15 → drop cookies,
  keep functional comments + docs/web-ui.md::Tab strip + gateway.md
  pointers for matrix
- #385 dropped C0NTAINERS heading → drop framing
- #460 reminders-moved-here → drop framing
- #444 SchedulesChanged SSE absence → drop cookie, keep inline why
- #443 selection bar → docs/web-ui.md::Selection bar pointer
- #564 fold-create-into-table → drop framing
- #369#issuecomment-3437 → drop attribution
- #406 step 3 bundle rename → drop history

flow.html (3 → 0):
- #389 slug + #362 pill pattern + #406 step 2 bundle → drop cookies,
  preserve functional descriptions

Total this batch (across all 4 files): **35 cookies scrubbed**.
Net effect: the dashboard SPA's HTML + JS comments all point at
docs/web-ui.md for substantive design context now, with inline
comments only retaining present-state operational descriptions.

frontend/packages/dashboard/src/common.js

@@ -1,13 +1,7 @@
-// Shared dashboard helpers — extracted from the original monolithic
-// dashboard JS as step 1 of the #406 split. These bits are used by
-// both the tab dashboard (index.html) and the flow page (flow.html):
-// pure DOM helpers, the side-panel singleton, the OS-notification
-// module, and the path-link / file-preview infrastructure for the
-// side panel.
-//
-// Each page now has its own entry point — `./tabs.js` for index.html,
-// `./flow.js` for flow.html — and both import from here directly
-// (#406 steps 2 + 3 complete; #406 closed).
+// Shared dashboard helpers used by both index.html (./tabs.js) and
+// flow.html (./flow.js): pure DOM helpers, the side-panel singleton,
+// the OS-notification module, and the path-link / file-preview
+// infrastructure for the side panel.
 
 import { linkify as termLinkify } from '@hive/shared/terminal.js';
 
@@ -57,31 +51,23 @@ export const form = (action, btnClass, btnLabel, confirmMsg, extra = {}, opts =
 // tied to its caller, so they don't generalise cleanly. We can lift
 // them when a second consumer needs the same shape.
 
-// ─── shared-worker SSE pipe (#448) ──────────────────────────────────────
-// Returns an EventSource-shaped object backed by a SharedWorker that
-// holds ONE upstream `new EventSource(url)` and fans events out to
-// every connected tab. Replaces direct `new EventSource(url)` at the
-// dashboard's two consumer sites (tabs.js inline + flow.js via
-// terminal.js's `streamFactory` option) so N hyperhive tabs share
-// ONE backend connection — way under the browser's per-host
-// connection cap, immune to per-tab throttling that drops the SSE
-// when Firefox suspends background tabs.
+// ─── shared-worker SSE pipe ─────────────────────────────────────────────
+// Returns an EventSource-shaped facade backed by a SharedWorker that
+// holds one upstream `new EventSource(url)` and fans events out to
+// every connected tab. See docs/web-ui.md (SSE multiplexing paragraph)
+// for the design + Firefox throttling motivation; graceful fallback to
+// direct EventSource on environments without SharedWorker.
 //
-// Graceful fallback to direct EventSource on environments without
-// SharedWorker (some embedded browsers, some Safari versions). The
-// per-tab connection cost is the same as today — no regression.
-//
-// The page consumer uses the returned object like a regular
-// EventSource: assign `onmessage` / `onopen` / `onerror`. `.close()`
-// tells the worker to drop the subscription; the worker closes the
-// upstream EventSource when the last subscriber leaves.
+// Consumer API: assign `onmessage` / `onopen` / `onerror`; `.close()`
+// drops the subscription (the worker closes the upstream when the last
+// subscriber leaves).
 const SHARED_WORKER_PATH = '/static/stream-worker.js';
 const SHARED_WORKER_NAME = 'hyperhive-stream';
 
 // One SharedWorker port per page, reused by all openStream calls on
 // that page. Invalidated on `pagehide` so a bfcache restore picks up
-// a fresh port (the cached one may have been collected if all other
-// tabs closed while this page was frozen — argus nit on #453).
+// a fresh port — the cached port may be dead if all other tabs
+// closed while this page was frozen.
 let _sharedPort = null;
 function makeSharedPort() {
   if (typeof SharedWorker === 'undefined') return null;
@@ -99,30 +85,11 @@ function getSharedPort() {
   return _sharedPort;
 }
 
-// #515: detect when the SharedWorker has been killed. Firefox aggressively
-// reclaims "idle" SharedWorkers under memory pressure (or just on tab
-// lifecycle quirks we don't fully understand), and there's no native
-// signal to the client when that happens — `postMessage` on a dead
-// port silently no-ops, and the page just stops receiving events. The
-// observable symptom is "dashboard never refreshes; F5 fixes it" (a
-// fresh page creates a fresh worker), which is mara's report on #515.
-//
-// Pipeline:
-//   - The worker pings every connected port every WORKER_PING_INTERVAL_MS.
-//   - `route` (every message arrival, including pings) bumps
-//     `_lastWorkerActivityAt`.
-//   - `startWorkerWatchdog` polls every WORKER_WATCHDOG_INTERVAL_MS.
-//     If the page is visible AND we have active subs AND we haven't
-//     heard from the worker in > WORKER_DEAD_THRESHOLD_MS, we presume
-//     the worker is dead, log a warning, and re-subscribe on a fresh
-//     port.
-//
-// Numbers picked so a real Firefox tab-suspend / unsuspend cycle (which
-// can pause the watchdog itself) doesn't false-positive: 90s without a
-// 30s ping means at least three pings missed. Visibility-gated so a
-// backgrounded tab — where Firefox throttles setInterval to 1Hz min and
-// our healthcheck wouldn't trigger reliably anyway — doesn't try to
-// reconnect uselessly.
+// SharedWorker death detection: pings from the worker bump the
+// activity clock; a visibility-gated watchdog polls and re-subscribes
+// on a fresh port if the page has been silent past the threshold.
+// See docs/web-ui.md (Worker-death self-heal paragraph) for the
+// timing rationale + Firefox reclaim symptom.
 const WORKER_DEAD_THRESHOLD_MS = 90_000;
 const WORKER_WATCHDOG_INTERVAL_MS = 15_000;
 let _lastWorkerActivityAt = 0;
@@ -164,25 +131,19 @@ function rebindOnFreshPort() {
   noteWorkerActivity();
 }
 
-// Registry of live subscriptions on this page. Keyed by url so a
-// second openStream call for the same URL (would only happen on a
-// hypothetical multi-consumer page) attaches to the existing route
-// rather than overlapping. Each entry caches the route function so
-// bfcache-restore re-bind can re-attach it to the fresh port.
-//
-// Today's pages only call openStream once with one URL; the registry
-// shape just keeps the bfcache-restore path correct if that changes
-// (e.g. /index.html later subscribing to two streams).
+// Registry of live subscriptions on this page. Keyed by url; entries
+// cache the route function so bfcache-restore re-bind can re-attach
+// it to the fresh port. Today's pages only call openStream once with
+// one URL; the registry shape just keeps the bfcache path correct
+// if that changes.
 const _activeSubs = new Map();
 
-// One-shot wiring of the page-wide lifecycle hooks: on bfcache
-// freeze (`pagehide { persisted: true }`) we unsubscribe so the
-// worker can close the upstream when the last live subscriber
-// leaves; on bfcache restore (`pageshow { persisted: true }`) we
-// invalidate the cached port (it may be dead if all other tabs
-// closed during the freeze) and re-attach every active subscription
-// to a fresh port. argus nit on #453: without this, the consumer's
-// onmessage stays bound but no events flow after a bfcache restore.
+// One-shot wiring of page-wide lifecycle hooks. On bfcache freeze
+// we unsubscribe so the worker can close the upstream when the last
+// live subscriber leaves; on bfcache restore we invalidate the cached
+// port (may be dead after the freeze) and re-attach every active
+// subscription to a fresh port. Without this, the consumer's
+// onmessage stays bound but no events flow after restore.
 let _lifecycleBound = false;
 function bindLifecycleOnce() {
   if (_lifecycleBound) return;
@@ -245,7 +206,7 @@ export function openStream(url) {
     },
   };
   const route = (e) => {
-    // #515: any message from the worker is proof of life — note it
+    // Any message from the worker is proof of life — note it
     // before the URL filter, since heartbeat pings carry no URL.
     noteWorkerActivity();
     const m = e.data;
@@ -272,8 +233,8 @@ export function openStream(url) {
   _activeSubs.set(url, { target, route });
   port.addEventListener('message', route);
   port.postMessage({ kind: 'subscribe', url });
-  // #515: seed the activity clock so the watchdog has a baseline; it
-  // would otherwise compare against 0 (epoch) and trigger immediately.
+  // Seed the activity clock so the watchdog has a baseline (would
+  // otherwise compare against 0 and trigger immediately).
   noteWorkerActivity();
   return target;
 }
@@ -330,13 +291,10 @@ export const Panel = (() => {
     root.classList.remove('open');
     root.setAttribute('aria-hidden', 'true');
   }
-  // #451: drag-to-resize the drawer's width. Listens on a thin
-  // hit-strip glued to the drawer's left edge; mousedown captures
-  // pointermove + pointerup on the document so the drag continues
-  // even if the cursor strays outside the 6px handle band. Width
-  // persists to localStorage so it survives page reload. The CSS
-  // clamps the value (min-width: 320px, max-width: 96vw) — drop
-  // unparseable / out-of-range stored values silently.
+  // Drag-to-resize the drawer's width. See docs/web-ui.md::Side panel
+  // for the hit-strip + pointer-capture + localStorage persistence
+  // model; CSS clamps the stored value to min 320px / max 96vw and
+  // out-of-range stored values are dropped silently.
   const WIDTH_KEY = 'hyperhive:side-panel-width';
   const WIDTH_MIN = 320;
   function clampWidth(w) {
@@ -476,7 +434,7 @@ function mdNode(text) {
     window.marked.setOptions({ breaks: true, gfm: true });
     div.innerHTML = window.marked.parse(text);
     // marked autolinks URLs but leaves them same-tab — open externally
-    // so a click never navigates away from the dashboard. (issue #233)
+    // so a click never navigates away from the dashboard.
     div.querySelectorAll('a[href]').forEach((a) => {
       a.target = '_blank';
       a.rel = 'noopener noreferrer';