feat(legal): add immutable source repair transaction

[zhengdaqi]

Summary

Adds a bounded immutable Legal Coverage repair transaction for rejected source-merge proposals. The repair is validated against the unchanged proposal and current state, applied through an exact command, and renews semantic progress only after a verified applied receipt.

This addresses the preserved Case 09 failure where two proposal facts needed corrections but the read/edit protocol exhausted the bounded Progress Lease.

Changes

• Derive a deterministic source-repair-<digest>.json contract from complete fact-level diagnostics.
• Reconstruct and validate the corrected full proposal internally without exposing it to the Agent prompt.
• Atomically project accepted source/fact rows and bind progress to source-repair-applied-<digest>.json.
• Observe the required write_file preparation checkpoint through PostToolUse without changing Core or Lease thresholds.
• Add fail-closed counterexamples, a real Gateway test, and a preserved Case 09 failure replay.

QA & Evidence

• Full repository suite: 308/308 passed after one isolated, non-reproducible O1 temp-directory cleanup race. See .omo/evidence/20260727-v24r8-immutable-source-repair/full-test-rerun.log and o1-isolated-rerun.log.
• Real local Gateway: 4/4 passed with Router and Memory disabled, O1 diagnostic/4096 complete, paired model/tool/turn events, and zero drops. See real-gateway.log.
• Preserved Case 09 source failure: preparation 0 -> 1 -> 1, progress 0 -> 0 -> 1, rejected proposal unchanged. See case09-replay-result.json.
• Reviewer-readable scope, commands, observations, sufficiency, omissions, and residual risk: .omo/evidence/20260727-v24r8-immutable-source-repair/QA.md.

Risks & Residuals

• The complete 35-minute production-model Case 09 product Gate has not run yet. V25 and the 85-case campaign remain blocked.
• The post-apply validator intentionally exposes more downstream matrix and coverage work; error-count reduction is not treated as semantic progress.
• No validator acceptance, taxonomy, Progress Lease 8/2, Router, Memory, O1, V24R7 authority closure, model, or corpus behavior changed.

Stack

This PR intentionally targets codex/convergence-v24r7-bounded-authority-closure, its exact dependency base, so the V24R8 review remains isolated from the preceding convergence stack.