run_apply_commit walks the approval through the tag state
machine in applied: approved/<id> + building/<id> stamped
before the build, then git read-tree --reset to proposal/<id>
populates the working dir without moving HEAD. on rebuild
success deployed/<id> is planted and refs/heads/main fast-
forwards to the proposal. on failure failed/<id> is annotated
with the build error and the working tree resets back to main
so the agent stays evaluable. helper events Rebuilt +
ApprovalResolved both carry the terminal tag so the manager
can git-show the exact tree (and read the failure note from
an annotated tag) against its read-only applied.git mount.
finish_approval grows a terminal_tag param; spawn path passes
None. lifecycle::apply_commit deleted.