fix(opencode): publish dispatch status evidence

[seonghobae]

Summary

• Publishes the workflow_dispatch OpenCode result as an opencode-review commit status from the GitHub Actions token.
• Keeps branch-protection evidence tied to the PR head SHA when manual dispatch is used as the central review fallback.
• Adds contract and quick-gate coverage so the status context, statuses: write permission, target commit status API, and logged description remain visible.

Context

PR #479 merged before this final follow-up commit reached main. This PR carries only that missed central governance fix on top of current main.

Verification

• codegraph init; codegraph sync; codegraph status
• git diff --check origin/main..HEAD
• py -3.12 -m pytest tests\\test_opencode_agent_contract.py tests\\test_opencode_workflow_shell_syntax.py tests\\test_pr_review_merge_scheduler.py tests\\test_opencode_model_pool_runner.py tests\\test_pr_head_replay_guard.py tests\\test_changed_file_syntax_gate.py tests\\test_pr_review_fix_scheduler_coverage.py -q => 129 passed, 2 skipped

[opencode-agent]

Pull request overview

OpenCode model providers were unavailable for this same-head run, but this PR is limited to the central review-process repair surface and the current-head evidence is clean.

Findings

No blocking findings.

Evidence

• Result: APPROVE
• Reason: central review-process evidence fallback after model provider unavailability; coverage, docstring, peer GitHub Checks, code-scanning alerts, mergeability, and review threads were clear for current head.
• Scope: central OpenCode/Strix review-process
• Changed files: 3
• Model-pool outcome: exhausted
• Head SHA: b391122be9d501dafb8ef0bffd5eb8b3abdf87a4
• Workflow run: 29198710093
• Workflow attempt: 1

This fallback is limited to central review-process self-repair and does not apply to application source, dependency manifest, lockfile, generated artifact, or documentation-only PRs.