feat(config): add review.path_filters include/negation glob knob

[JSONbored]

Add review.path_filters — an include + !-negation glob list that extends the existing exclude_paths so operators can positively scope the AI review to certain paths (with negations subtracting). Deterministic; empty (default) ⇒ every non-excluded file reviewed (byte-identical). Decomposed from #1959.

Deliverables

• Add pathFilters: string[] to FocusManifestReviewConfig in src/signals/focus-manifest.ts and parse review.path_filters (support leading ! negation entries)
• Apply after exclude_paths in the diff/grounding/RAG file-selection step (reuse the exclude-path filtering site near src/signals/focus-manifest.ts:940) so gate/slop/secret-scan stay unaffected
• Wire reviewConfigToJson round-trip + present + EMPTY literals
• Document the manifest glob rule (both * and ** cross slashes — see compileManifestPathMatcher) in the field doc-comment and .gittensory.yml.example
• Unit tests: include-only, negation-subtracts, interaction with exclude_paths, empty byte-identical; branch-counted coverage on the include/negate/empty arms

References

• src/signals/focus-manifest.ts:144 (excludePaths field)
• src/signals/focus-manifest.ts:774 (parseReviewExcludePaths)
• src/signals/focus-manifest.ts:940 (exclude filtering + compileManifestPathMatcher note)
• .gittensory.yml.example
• part of #1959 (epic #1953)

Part of #1959.

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size: M · gittensor:feature

[linear-code]

JSO-2160