feat(review): add review.auto_review config container + parseReviewConfig/reviewConfigToJson round-trip

[JSONbored]

Foundation for #1954: introduce a new review.auto_review sub-mapping on FocusManifestReviewConfig with an empty/default shape that round-trips through parseReviewConfig and reviewConfigToJson byte-identically when absent. No predicate logic yet — just the parsed container + a pure decideReviewEligibility(config, prFacts) shell that always returns eligible, so subsequent predicate PRs each add one branch. Default unset ⇒ every PR reviewed exactly as today.

Deliverables

• Add an autoReview field (typed shape with all predicate knobs defaulting to off/empty) to FocusManifestReviewConfig in src/signals/focus-manifest.ts:124
• Extend parseReviewConfig (src/signals/focus-manifest.ts:653) to parse review.auto_review as a mapping (warn + ignore on non-mapping), include it in the empty literal (src/signals/focus-manifest.ts:654) and the present computation (src/signals/focus-manifest.ts:681)
• Extend reviewConfigToJson (src/signals/focus-manifest.ts:835) to emit auto_review only when a knob is set (absent ⇒ omitted key ⇒ byte-identical)
• Add a pure decideReviewEligibility(autoReview, facts): { eligible: boolean; skipReason: string | null } shell (returns eligible=true always) in a new src/review/review-eligibility.ts module
• Unit tests: absent/empty round-trip is byte-identical, non-mapping warns+ignores, shell returns eligible; cover both branches of every ??/optional (97% branch-counted)

References

• src/signals/focus-manifest.ts:124
• src/signals/focus-manifest.ts:653
• src/signals/focus-manifest.ts:835
• #1954

Part of #1954.

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size: S · gittensor:feature

[linear-code]

JSO-2175