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.

docs/web-ui/README.md

@@ -16,13 +16,13 @@ surfaces — Stats, the API docs and the swarm UI — and each of
 those pages links back to the dashboard.
 
 The dashboard is where you'll spend most of your time. It's a single
-page with five tabs:
+page with four tabs:
 
 - **4G3NTS** — every agent, live. This is the default tab and the one
   you'll check most.
-- **R3BU1LD QU3U3**, **M3T4 1NPUTS** and **BUILD L0GS** — the build
+- **R3BU1LD QU3U3** and **BUILD L0GS** — the build
   lifecycle: the rebuild queue with a live log of whatever is building,
-  the meta flake inputs you can bump, and the build log history.
+  and the build log history.
 - **K3PT ST4T3** — kept state from agents with no container
   (tombstones), with a purge button per entry.