Add Automerge stable-red proof harness

[hxy91819]

Part 1 of the Automerge reliability improvement series.

What changed

• Adds a local-only Automerge E2E proof harness for flow, publication, runtime, and deterministic state-model scenarios.
• Binds candidate revisions, executable/dependency digests, fixture identity, proof summaries, and repeat inventories.
• Adds historical state-publication and OpenClaw runtime reproducer paths using only local bare remotes and a fake GitHub CLI.
• Adds the tracked English Automerge Reliability Improvement Plan, including a completed-work, blockers, and next-owner handoff checklist.

Safety

This PR does not modify production Automerge logic and does not perform live GitHub mutation. The harness uses disposable local fixtures, local bare Git remotes, and network isolation.

Validation

• Node syntax checks for the harness
• 23 focused proof/candidate/gate/model tests
• format check and diff check
• real git-hooks reproducer confirmation
• 10/10 publication and deterministic-model inventories

The plan explicitly records remaining process-leak and flow-digest work; they are not presented as completed evidence.

[clawsweeper]

ClawSweeper status: review started.

I am starting a fresh review of this pull request: Add Automerge stable-red proof harness This is item 1/1 in the current shard. Shard 0/1.

This placeholder means the worker is alive and reading the current context. I will edit this same comment with the actual review when the claws are done clicking.

Crustacean status: shell secured, claws on keyboard, evidence pebbles being sorted.