feat(builds): add /builds.html — build lifecycle hub (closes #1999)

New standalone page /builds.html consolidating rebuild queue, meta
inputs, and build log history into one place, with a new 'Builds' home
tile linking to it. Addresses mara's request: new sub-page with a new
home tile, all three items moved there.

Changes:
- builds.html: new page with three sub-tabs: R3BU1LD QU3U3, M3T4 1NPUTS,
  BUILD L0GS. Same minimal-chrome header + createTabStrip pattern as core
  and logs pages.
- builds.js: new bundle combining rebuild queue renderer (from core.js),
  meta inputs renderer (from core.js), rebuild-live-log renderer (from
  core.js), and build log history renderer (from logs.js). Deep-links to
  /builds.html?id=N#buildlogs. Count pill id: builds-tab-count-rebuild.
  BUILD L0GS tab lazy-loads on first activation.
- builds.css: @imports system-sections.css (rebuild queue + meta inputs +
  live-log styles) and logs.css (build-logs-* component styles).
- build.mjs: register builds.js, builds.css, builds.html.
- core.html: remove R3BU1LD QU3U3 + M3T4 1NPUTS tabs (now on builds.html).
  Default tab changes to K3PT ST4T3.
- core.js: remove renderMetaInputs, renderRebuildQueue + helpers,
  renderRebuildLiveLog + live-log state, elapsed-time tickers,
  updateRebuildCount, and the rebuild_queue/meta_inputs SSE handlers.
  Remove openBuildLogStream + util imports no longer needed.
- core.css: remove .rebuild-live-log-* rules (moved to system-sections.css
  so builds.css can share them via @import).
- system-sections.css: add .rebuild-live-log-* styles (moved from core.css);
  update comment to mention builds.html.
- logs.html: remove BUILD tab + pane (moved to builds.html).
- logs.js: remove fetchBuild(), fmtTs, fmtDuration, openBuildLogStream
  import, and rebuild_queue_changed SSE debounce. Default tab: 'agent'.
  SSE stream retained for audit_entry_added live-appends.
- index.html: add Builds tile (🔨, rebuild queue · meta inputs · build
  logs); update Core tile desc to 'kept state · container load'; update
  Logs tile desc to remove 'build'.

frontend/packages/dashboard/src/core.css

@@ -1,18 +1,21 @@
 /* ─── /core.html — C0R3 page ───────────────────────────────────────
-   Standalone page carved out of the dashboard's old SYST3M tab. Same
-   minimal-chrome pattern as /logs.html (a `← home` back-link + a
-   createTabStrip sub-tab strip; base tab + page-header styling comes
+   Standalone page for kept state (tombstones) and container load.
+   Same minimal-chrome pattern as /logs.html (a `← home` back-link +
+   a createTabStrip sub-tab strip; base tab + page-header styling comes
    from @hive/shared via common.css, linked by core.html).
 
-   The four section renderers (rebuild queue, meta inputs, kept state,
-   container load) are ported verbatim from the dashboard, so they emit
-   the exact same class names. Those section-internal rules live in
-   system-sections.css (shared with the dashboard, which references a
-   couple of them — `.rqe-source*` — from its schedules view). The
+   The section renderers (kept state, container load) emit the same
+   class names as before. Those section-internal rules live in
+   system-sections.css (shared with dashboard.css and builds.css, which
+   references `.rqe-source*` from the schedules view). The
    `.hive-stats-table` the container-load table reuses lives in
    common.css, linked directly by core.html. Importing just the section
    rules keeps the C0R3 bundle small instead of dragging in all of
-   dashboard.css. */
+   dashboard.css.
+
+   Rebuild queue + meta inputs have moved to /builds.html; the
+   `.rebuild-live-log-*` styles that used to live here have moved to
+   system-sections.css so builds.css can share them via @import. */
 @import "./system-sections.css";
 
 body.core-shell {
@@ -33,70 +36,3 @@ body.core-shell {
 /* createTabStrip toggles the native `hidden` attribute on inactive
    panes; ensure it wins over any inherited display. */
 .core-pane[hidden] { display: none; }
-
-/* ─── running-rebuild live log (renderRebuildLiveLog in core.js) ──────────
-   Streams the currently-running rebuild's build log inline under the queue.
-   Hidden (native `hidden` attr) when nothing is building. */
-.rebuild-live-log {
-  margin-top: 0.8em;
-  border: 1px solid var(--purple-dim);
-  border-radius: 4px;
-  background: color-mix(in srgb, var(--crust) 70%, transparent);
-}
-.rebuild-live-log-header {
-  display: flex;
-  align-items: center;
-  gap: 0.4em;
-  padding: 0.4em 0.6em;
-  font-size: 0.85em;
-  border-bottom: 1px solid var(--border);
-}
-.rebuild-live-log-toggle {
-  background: transparent;
-  border: 0;
-  color: var(--muted);
-  cursor: pointer;
-  font-family: inherit;
-  font-size: 1em;
-  padding: 0 0.2em;
-}
-.rebuild-live-log-toggle:hover { color: var(--fg); }
-.rebuild-live-log-title { color: var(--muted); }
-.rebuild-live-log-raw {
-  margin-left: auto;
-  color: var(--purple);
-  text-decoration: none;
-  font-size: 0.9em;
-}
-.rebuild-live-log-raw:hover { text-decoration: underline; }
-.rebuild-live-log-badge {
-  font-size: 0.75em;
-  font-weight: bold;
-  padding: 0.05em 0.5em;
-  border-radius: 999px;
-  letter-spacing: 0.05em;
-}
-.rebuild-live-log-badge.rll-running {
-  color: var(--amber);
-  background: color-mix(in srgb, var(--amber) 18%, transparent);
-}
-.rebuild-live-log-badge.rll-ok {
-  color: var(--green);
-  background: color-mix(in srgb, var(--green) 18%, transparent);
-}
-.rebuild-live-log-badge.rll-fail {
-  color: var(--red);
-  background: color-mix(in srgb, var(--red) 18%, transparent);
-}
-.rebuild-live-log-output {
-  margin: 0;
-  padding: 0.5em 0.7em;
-  max-height: 22em;
-  overflow-y: auto;
-  white-space: pre-wrap;
-  word-break: break-word;
-  font-family: "JetBrains Mono", "Fira Code", "Cascadia Code", "Source Code Pro", monospace;
-  font-size: 0.8em;
-  line-height: 1.4;
-  color: var(--fg);
-}