docs: use explicit contribution triage exemptions

[juliusmarminge]

Problem

Contribution triage currently requires private organization-membership access before it can close or hand off a PR. The available native GitHub events also cannot satisfy the skill's full event-coverage requirement.

Change

• Add .github/TRIAGE_EXEMPTIONS.td beside VOUCHED.td, with only juliusmarminge, maria-rcks, and t3dotgg.
• Resolve trusted upstream refs/heads/main afresh for every live run and read the skill, policy dependencies, and exemption list at that same SHA. Ignore PR/fork policy changes and fail closed if trusted files are unavailable or malformed.
• Permit the agreed partial native event coverage, fetching full current PR state for cumulative assessment on every supported event. No periodic sweep or new runner.
• Preserve the eligibility, state-recheck, comment-before-close, and deduplication safeguards. Exempt authors still need the verified macroscope-review handoff; the file does not itself trigger review. Existing vouched-contributor auto-review stays enabled during validation until a maintainer chooses to disable it.

Scope and approval

Maintainer-requested follow-up to #14480. Julius approved these three exemptions, partial event coverage, and staged coexistence with the existing auto-review. This changes only the list and its directly affected policy text. No workflows, Macroscope settings, or other PRs are changed.

Verification

• git diff --check: passed.
• Focused local consistency checks: exact sorted and unique exemption entries; valid login syntax; new policy links resolve; trusted-main and partial-event requirements present.
• Compared against upstream main: unrelated eligibility guidance, closure guidance, mutation rechecks, and retry safeguards are unchanged.
• Independent read-only policy review found no material gaps. Rechecked staged coexistence, trigger verification, and settings boundaries after the final wording change.
• vp fmt --check CONTRIBUTING.md .agents/skills/contribution-triage/SKILL.md was not run because vp is unavailable in the partial cloud snapshot. Application tests and repo-wide checks were not run locally for this policy-only change.
• CI on 8bf7712 passed Check (including formatting, typecheck, and desktop build), Test, all three server test shards, Rust, and Release Smoke. Mobile Native Static Analysis was skipped as intended because no native files changed.
• Branch base: 0d9468fea907dda747b51204e92ca15b54f81d47.

Model: OpenAI model (exact model ID not exposed). Harness: Codex, using the dot cloud workspace and GitHub connector.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.5 KiB	13.5 KiB	+29 B (+0.2%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	−1 B (−0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.5 KiB	6.5 KiB	+30 B (+0.5%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.3 KiB	56.3 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	10	10	0 (0.0%)	21	✅
Claude	Total thread wire	13.5 KiB	13.5 KiB	+3 B (+0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	−3 B (−0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.4 KiB	6.4 KiB	+6 B (+0.1%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.0 KiB	57.0 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: 0d9468f · PR result: 8bf7712 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 113.9 KiB
• Claude decoded thread snapshot: 114.7 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.