Recover missing CommandFinished hooks from Precmd completion metadata

[vorporeal]

Description

Stack PR 7/8; depends on #12857.

Context

A dropped CommandFinished is the key recoverable failure this stack targets. The shell can finish a command and emit Precmd, while Warp still believes the old block is submitted or executing. Without trustworthy completion evidence, advancing would require inventing an exit code or next-block identity; not advancing leaves the controller and block model stuck and risks applying the new prompt to the old command block.

The earlier stack PRs make recovery safe: #12853 gives Precmd the real completion identity, #12854 distinguishes Precmd hooks with completion metadata from prompt-only Precmd hooks, #12855 provides one completion pipeline, #12856 gates every transition, and #12857 makes prompt application and refresh safe.

Approach

When a Precmd with completion metadata carries a novel next block ID, the coordinator now treats it as completion evidence. It runs the same completion pipeline used by CommandFinished with the shell-provided exit code and exact next block ID, then applies the received prompt metadata only to the fresh block. If the active block was already finished, the model advances without finishing or emitting completion again; if Warp missed earlier start/pre-execution evidence, it performs the minimal transition needed to preserve truthful completed-block state.

All non-normal state-mutating recovery remains behind TerminalLifecycleRecovery. Duplicate, stale, or colliding completion metadata, partial payloads, and prompt-only evidence still cannot trigger completion. Shared-session and version-skew paths preserve the same conservative rules.

Review guidance

• Does recovery use only the shell-provided exit code and next block ID from completion metadata, without guessing or accepting weaker evidence?
• Does recovered completion preserve the normal cleanup/event ordering and emit every once-per-block side effect exactly once?
• Is prompt metadata applied only after advancing to the fresh block?
• Do feature-flag and shared-session/version-skew boundaries prevent unsupported clients from taking the recovery path?

Testing

• Added model recovery-matrix and shared-session old-sharer/new-viewer compatibility coverage.
• Added an all-shell real-shell regression that suppresses CommandFinished; confirmed it fails on the preceding PR and passes here.
• Final-stack validation: focused lifecycle tests, cargo check -p warp --tests, ./script/format, and git diff --check.

[vorporeal]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Enable terminal lifecycle recovery in dogfood #12859
• Recover missing CommandFinished hooks from Precmd completion metadata #12858 👈 (View in Graphite)
• Safely reconcile repeated and prompt-only Precmd hooks #12857
• Gate terminal lifecycle transitions with a coordinator #12856
• Centralize terminal lifecycle mutations #12855
• Distinguish Precmd hooks with completion metadata from prompt-only hooks #12854
• Add command completion metadata to Precmd #12853
• Document terminal block lifecycle hardening design #12852
• master

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