dashboard: replace <hive-jobq-graph> with a shared Preact component

Ports the shadow-DOM <hive-jobq-graph> custom element
(frontend/packages/shared/src/jobq-graph/) to a Preact component
(JobqGraph.js) shared by the dashboard and swarm-ui, per hyperhive#3310.

- JobqGraph.js: written with plain h() calls (no JSX) so the same file
  compiles unmodified under both the dashboard's text-loader CSS config
  and swarm-ui's JSX config. Exports `JobqGraph` for JSX use and
  `mountJobqGraph(container, props)` for the dashboard's non-JSX
  imperative mount, returning a `{refresh(), update()}` handle matching
  the old custom element's public surface. Same rendering contract as
  before: indented state tree, payload.label verbatim, payload.data as
  a generic key/value list, "waits on: <label>" text for Node-kind deps,
  per-state filter checkboxes, optional cancel button.
- jobq-graph.css: light-DOM adaptation of the old shadow-scoped
  stylesheet (:host -> .jg-root, otherwise unchanged).
- dashboard/src/builds.js: local mountJobqGraph() renamed to
  mountRebuildQueue() to avoid colliding with the newly-imported shared
  mountJobqGraph; cancel handling is now a plain onCancel callback
  instead of a DOM CustomEvent listener (no shadow boundary to cross
  anymore).
- dashboard + shared package.json: added preact as a dependency (matches
  swarm-ui's existing pin, 10.29.8) - the dashboard was a vanilla-JS MPA
  with no Preact/JSX pipeline before this.
- Removed the old hive-jobq-graph.js/.css entirely (confirmed via grep
  it had exactly one consumer, dashboard/src/builds.js, so this is a
  clean swap, not parallel maintenance of two implementations).
- Updated stale doc-comment references to the old element name in
  builds.html, tabs.js, swarm.js, docs/web-ui/dashboard.md, and
  hive-c0re/src/job_queue/mod.rs.

Verified: npm run build (whole frontend workspace) and npm run
typecheck (swarm-ui) both clean; cargo build/clippy/test -p hive-c0re
all clean (331 tests, 0 failures); headless-chromium screenshot of
/builds.html against a mock GET /api/jobq/graph payload confirms full
visual/behavioral parity with the old custom element (tree, filter
checkboxes, cancel buttons, error text, waits-on line, data list, live
build log panel).

This covers the dashboard-replacement half of hyperhive#3310 only. The
swarm-ui half (rendering the CreateAgent DAG on the agent-creation page)
is downstream of hyperhive#3306/#3124 landing - no swarm-ui page exists
yet to mount it in.

docs/web-ui/dashboard.md

@@ -228,16 +228,18 @@ not the graph.
 **R3BU1LD QU3U3** — pending, in-flight, and recently-settled container
 operations: rebuilds, meta-update cascades, and first-spawns. One
 operation runs at a time; the worker drains FIFO. **Is a mounted
-`<hive-jobq-graph endpoint="/api/jobq/graph">`** (the shared generic
-graph-viewer component, `@hive/shared/jobq-graph.js`) — `builds.js`
-does not render the queue itself; it just mounts the element and
-listens for its `hive-jobq-graph-update` event to drive the two things
-below it that the generic view doesn't show. The component owns
-fetching, cold and live: `GET /api/jobq/graph` on mount, and
-`.refresh()` on every `rebuild_queue_changed` SSE tick (that event is a
-bare `{ seq }` trigger — it carried a typed queue snapshot until every
-consumer had moved to the generic endpoint, and now carries none; both
-dashboard pages treat the tick as a pure refetch trigger).
+`JobqGraph`** (the shared generic graph-viewer Preact component,
+`@hive/shared/jobq-graph.js` — the same one swarm-ui uses, a Preact port
+of the former shadow-DOM `<hive-jobq-graph>` custom element) — `builds.js`
+does not render the queue itself; it just mounts the component
+(`mountJobqGraph(container, props)`, since this page has no JSX
+pipeline) with an `onUpdate` callback to drive the two things below it
+that the generic view doesn't show. The component owns fetching, cold
+and live: `GET /api/jobq/graph` on mount, and a refetch via the mount
+handle's `.refresh()` on every `rebuild_queue_changed` SSE tick (that
+event is a bare `{ seq }` trigger — it carried a typed queue snapshot
+until every consumer had moved to the generic endpoint, and now carries
+none; both dashboard pages treat the tick as a pure refetch trigger).
 
 Each row is one root graph node (`parent: null`); a multi-step op's
 per-agent subgraphs and sub-steps render as nodes within that one
@@ -250,10 +252,10 @@ as a plain "waits on: `<label>`" text line under the row rather than a
 gutter rail — a rail breaks visually whenever a nested subtree sits
 between the two related rows, since a text line needs no continuous
 vertical space to draw.
-`builds.js` mounts the element with `cancellable` set, which turns on
+`builds.js` mounts the component with `cancellable` set, which turns on
 a per-node cancel button (`✕`) on any non-terminal row — the button
-dispatches `hive-jobq-graph-cancel`, and the page does the actual
-`POST /api/rebuild-queue/{id}/cancel`, matching the wire event as its
+calls the mount's `onCancel(id)` callback, and the page does the actual
+`POST /api/rebuild-queue/{id}/cancel`, matching that callback to its
 own domain concept (the component knows nothing about that endpoint).
 **Rows carry no source chip, kind label, timing, or build-log
 deep-link** — the generic graph wire doesn't carry those fields, and
@@ -266,7 +268,7 @@ does not filter `Done` nodes out.
 the tree — one per lifecycle state, matching the row glyphs — lets the
 operator narrow which root groups render; unchecking a state re-fetches
 `GET /api/jobq/graph?states=<checked, comma-joined>` rather than
-hiding rows client-side, so `hive-jobq-graph-update`'s node list (and
+hiding rows client-side, so the `onUpdate` callback's node list (and
 everything downstream of it — the count pill, the live-log panel) only
 ever sees what's actually shown. Filtering is by a **root's own**
 state, which is already its subtree's rolled-up answer, so a group is
@@ -284,16 +286,16 @@ Below the queue, a **live build-log panel** (`#rebuild-live-log`,
 `renderRebuildLiveLog`) shows the currently-running rebuild's output
 inline — collapsible, with a live/ok/fail badge and a `↓ raw`
 download. It's keyed to the first `Running` node (in wire order)
-whose `payload.data.build_log_id` is set — read from the
-`hive-jobq-graph-update` event's node list, same source as the count
-pill, no separate fetch — and **polls** `GET /api/build-log/{id}`
-every 2s (`fetchAndRenderLiveLog` / `liveLogPollTimer`); not an
-`EventSource` (that's the BUILD L0GS tab's own per-row expand view
-below — `GET /api/build-logs/id/{id}/stream`, real SSE, replays
-accumulated output on connect — a separate mechanism). The live-log
-panel lives in its own container outside `#rebuild-queue-section` so
-the mounted `<hive-jobq-graph>`'s own re-renders never disturb the
-open poll; it hides when nothing is building.
+whose `payload.data.build_log_id` is set — read from the `onUpdate`
+callback's node list, same source as the count pill, no separate
+fetch — and **polls** `GET /api/build-log/{id}` every 2s
+(`fetchAndRenderLiveLog` / `liveLogPollTimer`); not an `EventSource`
+(that's the BUILD L0GS tab's own per-row expand view below — `GET
+/api/build-logs/id/{id}/stream`, real SSE, replays accumulated output
+on connect — a separate mechanism). The live-log panel lives in its
+own container outside `#rebuild-queue-section` so the mounted
+`JobqGraph`'s own re-renders never disturb the open poll; it hides
+when nothing is building.
 
 **M3T4 1NPUTS** — inputs in `meta/flake.lock` the operator can
 selectively `nix flake update`, rendered as an indented tree: