feat(config): add review.memory (features flag) for repeat false-positive suppression

[JSONbored]

Config slice for #1964: the per-repo default-OFF toggle that gates the whole review-memory subsystem, wired through the features:/review config with a global env kill-switch, byte-identical when unset. Enables the record/apply slices to guard on a single resolved flag.

Deliverables

• Add reviewMemory: boolean|null to FocusManifestReviewConfig (or a features: key) + parse/normalize, default null
• isReviewMemoryEnabled(env) kill-switch helper following the isInlineCommentsEnabled precedent
• Resolver helper AND-ing manifest toggle + env flag
• Tests: manifest/env combinations, absent defaults, both branches

References

• src/signals/focus-manifest.ts:131
• src/signals/focus-manifest.ts:47
• src/review/inline-comments.ts:21

Part of #1964.

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size: XS · held for later release (gittensor:bug once activated)

[linear-code]

JSO-2280