The config-PR deploy's apply node still did the whole container rebuild
inline, through the last surviving `lifecycle::rebuild_no_meta` call. It
now merges, opens the two-phase meta deploy, and returns the ordinary
rebuild chain as a subgraph the scheduler grafts into the live DAG under
it. A new `FinalizeDeploy` node, gated on that graft, plants the deploy
tag and commits the staged lock.
Net effect: "did the agent come back up?" is answered by `Reconcile`
succeeding, the same way it is for every other rebuild, instead of by a
fused inline start — and each deploy phase is its own queue node, so the
dashboard shows which one is running.
The grafted nodes root on the apply node, so they land inside
`DeployWindow`'s subtree and re-enter the meta window and build slot it
already holds rather than deadlocking against them. The new happy-path
test runs on a one-slot queue specifically to pin that down.
`FinalizeDeploy`'s two git writes are fatal, deliberately: they are what
tells `DeployTail` a deploy confirmed good, so a node that merely warned
on them could report success while leaving the tail looking at the git
state of a failure — and the tail would then roll a good deploy back.
The trailing `meta::finalize_deploy` stays warn-only, since by then the
container already runs the new config.
The `failed/<id>` annotated tag moves into the tail, which is now the
only place holding a failed deploy. It reads the reason off the DAG via
a new `JobQueue::first_error`, and is gated on `main` having actually
moved — the rollback ref is parked *before* the merge, so its existence
alone does not mean a merge happened, and a pre-merge rejection must not
tag the previous, innocent head.
Removing the last inline rebuild orphaned a chain of now-dead code:
`rebuild_no_meta`, `container_exists`, `Coordinator::set_queue_build_log`
and `JobQueue::set_build_log_id_running`, all deleted here.
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