docs(release-service): select historical ingest source

[ascorbic]

What does this PR do?

Completes Gate 0B by selecting raw com.atproto.sync.subscribeRepos commit events as the historical policy source and recording the required trust model, retained CAR/MST proof slice, ordering rules, backfill limits, and gap behavior for W10.1.

Related: #1908

Type of change

• Bug fix
• Feature (requires maintainer-approved Discussion)
• Refactor (no behavior change)
• Translation
• Documentation
• Performance improvement
• Tests
• Chore (dependencies, CI, tooling)

Checklist

• I have read CONTRIBUTING.md
• pnpm typecheck passes
• pnpm lint passes
• pnpm test passes (or targeted tests for my change)
• pnpm format has been run
• I have added/updated tests for my changes (if applicable). N/A, planning documentation only.
• User-visible strings in the admin UI are wrapped for translation (if applicable). N/A, no admin UI strings.
• I have added a changeset (if this PR changes a published package). N/A, planning documentation only.
• New features link to an approved Discussion: N/A, records the implementation decision for Delegated release service #1908.

AI-generated code disclosure

• This PR includes AI-generated code — model/tool: OpenCode with GPT-5.6 Sol and independent research/review agents

Screenshots / test output

The source decision was independently checked against current ATProto repository, event-stream, sync, backfill, Jetstream, and PLC behavior. Final technical review found no substantive issues.

[changeset-bot]

⚠️ No Changeset found

Latest commit: b8937e1

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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