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's render_flake and the pieces it needs (AgentSpec, AgentPin,
pinned_git_url, the forwarded-var tables, canonical_inputs_in_lock) move
into a new crate with no IO. The forwarded values and the GitHub switch
are now arguments; hive-c0re passes what it read from its own unit env,
as before. Nothing changes on deploy: the rendered flake is byte-for-byte
the same, and hive-c0re's render tests pass unchanged.
Refs #4857
