dashboard: the build pages are tabs of the dashboard

The build lifecycle used to be its own page with three sub-tabs. They are
now dashboard tabs (rebuild, meta, buildlogs) beside SW4RM and
P3RM1SS10NS: builds.js is a module tabs.js imports, so the dashboard's one
tab strip, /api/state snapshot and event stream (plus the meta_inputs_changed
and meta_update_running kinds) serve them, and the page, its bundle entry,
stylesheet and home tile are gone. The SW4RM banner's "view queue" link
points at the #rebuild tab, and the rebuild tab carries a count pill of the
rebuilds in flight.

An empty tab-count pill drew a "0": its display beat the UA [hidden] rule.

frontend/packages/dashboard/src/core.html

@@ -14,7 +14,8 @@
     <!-- C0R3: the host/coordinator surface. Standalone page (served at
        /core.html) carved out of the dashboard's old SYST3M tab so the
        dashboard tab strip stays lean: kept state (tombstones) and the
-       stale permission entries. The section <div> ids (tombstones-section,
+       stale permission entries. Rebuild queue + meta inputs are tabs of
+       /dashboard.html. The section <div> ids (tombstones-section,
        tombstones-stale-perms) match what core.js's renderers target. Hive
        infra containers (`hive-forge`, `hive-gateway`, `hive-matrix`) have
        no dashboard panel — `hivectl stop`/`start`/`restart` is the only