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.

hive-c0re/src/job_queue/mod.rs

@@ -1,7 +1,7 @@
 //! Generic job-DAG queue + desired-state reconciliation — the host-side
 //! wrapper over the domain-agnostic [`hive_jobq`] scheduler. Jobs are nodes in
 //! per-request DAGs (see [`templates`]); the special cases (graceful-stop
-//! watcher, deferred-start follow-up, meta-update cascade) collapse into DAG
+//! watcher, deferred-start follow-up) collapse into DAG
 //! *shapes* over the shared node primitives ([`model::NodeKind`]).
 //!
 //! [`hive_jobq`] owns the graph, the two-class resource pool, and the roll-up
@@ -327,7 +327,7 @@ impl JobQueue {
                 // without declaring its lease, and they are work on that agent
                 // that the operator wants to see.
                 //
-                // Empty means an agentless container kind (`MetaLock`, `Dag`),
+                // Empty means an agentless kind (the sweeps and pulls),
                 // which targets no agent and lights nothing.
                 let agent = n.payload.agent();
                 if agent.is_empty() {