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/swarm/archetypes.md

@@ -116,12 +116,11 @@ rebuild, and keeps the last value read in
 without the queue. When the read fails, a rebuild keeps the value
 stored there. For an archetype agent the hive:
 
-- seeds no `proposed` or `applied` repo, and gives the meta flake no
+- seeds no `proposed` or `applied` repo, and gives `internal/meta` no
   `agent-<name>` input. `mkAgent` imports
   `hyperhive.hyperhiveArchetypes.<name>.module` in place of the agent's own
   flake, and sets `HIVE_ARCHETYPE` in the harness environment;
-- relocks no agent input on a rebuild or a meta-input bump, and ignores the
-  `rev` of a swarm deploy request;
+- ignores the `rev` of a swarm deploy request;
 - mounts an empty `/agents/<name>/config/`.
 
 The agent's system prompt says it has no config repo and names its