refactor(frontend): extract the page-chrome into @hive/shared (#1464 step 3)

The standalone pages (/flow, /logs, /stats, /settings) all share the same
sticky back-link header, but its CSS lived in the dashboard's common.css
under the misnomer `.logs-*` (the comment even noted it was used by more
than logs). Promote it to a first-class shared component.

- new @hive/shared/chrome.css with neutral `.page-header` / `.page-back` /
  `.page-title` (cohering with the `.page-content` gutter wrapper);
  exported from the shared package and @imported into common.css next to
  base/terminal/tabs.css.
- rename the four pages' header markup `.logs-*` → `.page-*`.
- drop the old `.logs-*` chrome block from common.css; refresh the stale
  doc comments in settings.css / stats.css / dashboard.css.

CSS-only, behaviour/visual-neutral (same rules, new names + home). The
dashboard keeps its own richer sticky `.dashboard-chrome`; unifying the
per-agent UI's `.stats-nav` chrome is a larger follow-up, deferred.

Part of #1464 step 3.

frontend/packages/dashboard/src/common.css

@@ -3,6 +3,7 @@
 @import "@hive/shared/base.css";
 @import "@hive/shared/terminal.css";
 @import "@hive/shared/tabs.css";
+@import "@hive/shared/chrome.css";
 
 /* ─── global typography ─────────────────────────────────────────────
    Element-level rules shared across all three pages (index, flow,
@@ -220,38 +221,9 @@ code {
   color: var(--fg);
 }
 
-/* ─── page chrome: header + back link (flow + logs pages) ───────────
-   .logs-header / .logs-back / .logs-title are used by both
-   /flow.html and /logs.html — the same frosted sticky bar pattern. */
-.logs-header {
-  position: sticky;
-  top: 0;
-  z-index: 25;
-  background: color-mix(in srgb, var(--bg) 92%, transparent);
-  -webkit-backdrop-filter: blur(8px) saturate(120%);
-  backdrop-filter: blur(8px) saturate(120%);
-  border-bottom: 1px solid var(--purple-dim);
-  display: flex;
-  align-items: center;
-  gap: 1.5em;
-  padding: 0.5em 1.5em;
-}
-
-.logs-back {
-  color: var(--purple);
-  text-decoration: none;
-  font-size: 0.88em;
-  white-space: nowrap;
-  flex: none;
-}
-.logs-back:hover { text-decoration: underline; }
-
-.logs-title {
-  color: var(--subtext0);
-  font-size: 0.85em;
-  letter-spacing: 0.05em;
-  flex: none;
-}
+/* page chrome (.page-header / .page-back / .page-title — the standalone
+   pages' sticky back-link bar) moved to @hive/shared/chrome.css, imported
+   at the top of this file. */
 
 /* ─── operator inbox + message rows ────────────────────────────────
    .inbox and .msg-* are rendered by common.js (renderInbox) and

frontend/packages/dashboard/src/dashboard.css

@@ -32,9 +32,10 @@ body.dashboard-shell {
   margin: 0 0 1em;
 }
 /* ← home back-link to the H0M3 hub. Small purple link top-left of the
-   chrome, mirroring the .logs-back treatment the sub-pages use so the
-   navigation reads consistently. Full chrome unification (a shared,
-   reusable tab/back-link component) is a later step. */
+   chrome, mirroring the .page-back treatment the standalone pages use
+   (now shared from @hive/shared/chrome.css) so the navigation reads
+   consistently. The dashboard keeps this richer sticky chrome of its
+   own rather than folding into the simple page header. */
 .dash-home-back {
   display: inline-block;
   color: var(--purple);

frontend/packages/dashboard/src/flow.html

@@ -16,9 +16,9 @@
        No full tabbar — the flow page is a dedicated full-viewport
        terminal surface; navigating back to the menu is the only chrome
        needed. Pages link back to H0M3, not the dashboard. -->
-  <header class="logs-header">
-    <a class="logs-back" href="/">← home</a>
-    <span class="logs-title">FL0W</span>
+  <header class="page-header">
+    <a class="page-back" href="/">← home</a>
+    <span class="page-title">FL0W</span>
     <select id="flow-agent-filter" class="flow-filter" title="filter timeline by agent" aria-label="filter timeline by agent">
       <option value="">all agents</option>
     </select>

frontend/packages/dashboard/src/logs.html

@@ -15,8 +15,8 @@
   <!-- Minimal chrome: back link + sub-tab strip.
        Same pattern as flow.html — no full dashboard tabbar. Back link
        points to the H0M3 hub (served at /), not the dashboard. -->
-  <header class="logs-header">
-    <a class="logs-back" href="/">← home</a>
+  <header class="page-header">
+    <a class="page-back" href="/">← home</a>
     <nav class="hive-tabbar logs-tabbar" id="logs-tabbar" role="tablist">
       <a class="hive-tab" id="logs-tab-build" href="#build" role="tab"
          aria-controls="logs-pane-build" data-tab="build">

frontend/packages/dashboard/src/settings.css

@@ -1,9 +1,9 @@
 /* ─── /settings.html — operator-local preferences ──────────────────
    Extracted from the dashboard S3TT1NGS tab. Same
    minimal-chrome pattern as /flow.html and /logs.html: the back-link
-   header + title (.logs-header / .logs-back / .logs-title) live in
-   common.css; only the page body padding + the notif-toggle row are
-   page-specific and live here. */
+   header + title (.page-header / .page-back / .page-title) live in
+   @hive/shared/chrome.css; only the page body padding + the notif-toggle
+   row are page-specific and live here. */
 
 body.settings-shell {
   margin: 0;

frontend/packages/dashboard/src/settings.html

@@ -15,9 +15,9 @@
   <!-- Minimal chrome: back link + title. Same pattern as flow.html /
        logs.html — no full dashboard tabbar. Back link points to the
        H0M3 hub (served at /), not the dashboard. -->
-  <header class="logs-header">
-    <a class="logs-back" href="/">← home</a>
-    <span class="logs-title">S3TT1NGS</span>
+  <header class="page-header">
+    <a class="page-back" href="/">← home</a>
+    <span class="page-title">S3TT1NGS</span>
   </header>
 
   <main class="settings-main">

frontend/packages/dashboard/src/stats.css

@@ -1,7 +1,8 @@
 /* ─── /stats.html — hive-wide turn-stats rollup ────────────────────
    Extracted from the dashboard ST4TS tab. Same minimal-
    chrome pattern as /flow.html and /logs.html: the back-link header +
-   title (.logs-header / .logs-back / .logs-title) live in common.css.
+   title (.page-header / .page-back / .page-title) live in
+   @hive/shared/chrome.css.
    `.hive-stats-table` also lives in common.css — it's shared with the
    dashboard SYST3M › C0NT41N3R L04D table. Only the ST4TS-specific
    window selector, summary chips, and bars are page-specific. */

frontend/packages/dashboard/src/stats.html

@@ -15,9 +15,9 @@
   <!-- Minimal chrome: back link + title. Same pattern as flow.html /
        logs.html — no full dashboard tabbar. Back link points to the
        H0M3 hub (served at /), not the dashboard. -->
-  <header class="logs-header">
-    <a class="logs-back" href="/">← home</a>
-    <span class="logs-title">ST4TS</span>
+  <header class="page-header">
+    <a class="page-back" href="/">← home</a>
+    <span class="page-title">ST4TS</span>
   </header>
 
   <main class="stats-main">

frontend/packages/shared/package.json

@@ -13,7 +13,8 @@
     "./colors.css": "./src/colors.css",
     "./theme.css": "./src/theme.css",
     "./base.css": "./src/base.css",
-    "./terminal.css": "./src/terminal.css"
+    "./terminal.css": "./src/terminal.css",
+    "./chrome.css": "./src/chrome.css"
   },
   "files": [
     "src/"

frontend/packages/shared/src/chrome.css

@@ -0,0 +1,45 @@
+/* ─── page chrome: back-link header ────────────────────────────────
+   The minimal sticky "frosted bar" header used by every standalone page
+   reached from the H0M3 hub — /flow, /logs, /stats, /settings. A back
+   link to H0M3 on the left, then either a page title or (on /logs) a
+   createTabStrip sub-tab nav. The operator dashboard uses its own richer
+   sticky chrome (`.dashboard-chrome`); these classes cover the simple
+   pages.
+
+   Shared across packages via @hive/shared so a new page only links the
+   stylesheet + writes the three-element header markup:
+
+     <header class="page-header">
+       <a class="page-back" href="/">← home</a>
+       <span class="page-title">TITLE</span>
+     </header>
+*/
+.page-header {
+  position: sticky;
+  top: 0;
+  z-index: 25;
+  background: color-mix(in srgb, var(--bg) 92%, transparent);
+  -webkit-backdrop-filter: blur(8px) saturate(120%);
+  backdrop-filter: blur(8px) saturate(120%);
+  border-bottom: 1px solid var(--purple-dim);
+  display: flex;
+  align-items: center;
+  gap: 1.5em;
+  padding: 0.5em 1.5em;
+}
+
+.page-back {
+  color: var(--purple);
+  text-decoration: none;
+  font-size: 0.88em;
+  white-space: nowrap;
+  flex: none;
+}
+.page-back:hover { text-decoration: underline; }
+
+.page-title {
+  color: var(--subtext0);
+  font-size: 0.85em;
+  letter-spacing: 0.05em;
+  flex: none;
+}