[GP5-S4] Process-Kill Crashpoint Runner

[flyingrobots]

Roadmap slice: GP5-S4
Goalpost: Goalpost 5: Unified Bootstrap And Replay
Parent: #526
Related: #521, #522, #519, #510, #517

Source: docs/design/wal-wsc-durability-roadmap.md on branch cycle/521-wal-wsc-storage-relationship at bde7957c.

Scope

Parent issues:
#526,
#524.

Scope:

• Promote the current process.kill.after_wal_commit future descriptor into a
  real process-level crashpoint witness.

Acceptance:

• A child process commits WAL material, exits before publication, and a parent
  process recovers the committed history.
• A crash before commit does not appear as accepted/decided history.

Witness:

cargo test -p echo-dind-tests wal_process_crashpoints

Dedupe note

This is the PR-sized implementation slice for the roadmap item above. Existing umbrella or adjacent issues remain linked as Parent/Related rather than duplicated here.

[coderabbitai]

🔗 Related PRs

#309 - feat: add Doghouse PR flight recorder [merged]
#322 - feat: add witnessed suffix admission shell skeleton [merged]
#323 - Witnessed suffix admission evaluator [merged]
#329 - Stack Witness 0001 fixture-backed jedit walking skeleton [merged]
#379 - feat(core): commit runtime WAL ACK evidence [merged]

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