feat(config): add review.auto_review.auto_pause_after_reviewed_commits knob

[JSONbored]

Add review.auto_review.auto_pause_after_reviewed_commits (int, 0 = off) — after N reviewed commits on a PR, pause further AI re-reviews to cap re-review spend on churny PRs. Deterministic; 0/unset ⇒ byte-identical (re-review on every sync). Last of the #1954 eligibility filters.

Deliverables

• Add autoPauseAfterReviewedCommits: number | null to the autoReview sub-object in src/signals/focus-manifest.ts, parsed as a non-negative integer (reuse normalizeOptionalScore-style bounds validation; warn+ignore on negatives/non-ints)
• Wire parse + reviewConfigToJson + present + EMPTY literals
• Entry-point evaluation: when the count of already-reviewed commits on the PR reaches the threshold, post a quiet 'review paused (commit threshold)' status and skip the AI review, never a gate failure
• Unit tests: 0=off byte-identical, threshold reached vs not, negative/non-int warning; branch coverage on all arms
• Document under review.auto_review.auto_pause_after_reviewed_commits in .gittensory.yml.example

References

• src/signals/focus-manifest.ts:426 (normalizeOptionalScore numeric-bounds pattern)
• src/signals/focus-manifest.ts:653 (parseReviewConfig)
• .gittensory.yml.example
• part of #1954 / #1959 (epic #1953)

Part of #1954.

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size: S · gittensor:feature

[linear-code]

JSO-2159