build agents only from internal/meta; delete the hive's local meta flake

The hive no longer renders, locks or commits a meta flake. A rebuild's
MetaSync node picks the internal/meta commit and records it with the
hyperhive and config pins it holds; Prebuild, Swap and Create build from it,
and a head that does not pin the agent's current config fails the build
naming the agent. hive-priv's meta_rev is required.

Removed: meta.rs sync/lock/render, the manual-rebuild relock, the boot
sweep's hyperhive bump (MetaLock), the update-meta-inputs form and its
panel, MetaWindow, the hive's hyperhive_rev setting.

Kept: agent_set::refresh holds what sync_agents also did (topology.json, the
gateway's agent-socket map and nginx include), called from spawn, destroy,
rebuild and the migration.

The boot reconcile and the stale-start upgrade compare the agent's marker
with the hyperhive pin of internal/meta; the dashboard's deployed chip reads
the config marker a successful build writes.

frontend/packages/dashboard/src/dashboard.css

@@ -2,7 +2,7 @@
    it defines the CSS custom properties, typography, and shared
    component rules that this file depends on. */
 
-/* SYST3M panel rules (rebuild queue / meta inputs / kept state)
+/* SYST3M panel rules (rebuild queue / kept state)
    live in system-sections.css. */
 @import "./system-sections.css";
 @import "@hive/shared/jobq-rollup.css";
@@ -674,7 +674,7 @@ body.dashboard-shell.has-selection {
    shared `.hive-stats-table` moved to common.css. */
 
 /* ─── build tabs (builds.js) ────────────────────────────────────────
-   R3BU1LD QU3U3 and M3T4 1NPUTS are styled by system-sections.css and
+   R3BU1LD QU3U3 is styled by system-sections.css and
    jobq-graph.css; the BUILD L0GS list rules are below. */
 
 .logs-toolbar {