feat(config): add review.linkedIssueSatisfaction config knob (off/advisory/block, default off)

[JSONbored]

Wire the config-as-code knob for #1961 through the FocusManifestReviewConfig parse path only — parse + normalize + default-OFF, byte-identical when unset. This is the config slice; it does NOT touch the merge/close DECISION (that maintainer-only slice reads the resolved mode). Ships the .gittensory.yml parity in the same PR per the config-as-code rule.

Deliverables

• Add linkedIssueSatisfaction: 'off'|'advisory'|'block'|null to FocusManifestReviewConfig with a normalizeOptionalEnum parse and default null in src/signals/focus-manifest.ts
• Extend EMPTY_MANIFEST review block + the empty-manifest fallback so unset = byte-identical (src/signals/focus-manifest.ts:283)
• Warning-on-malformed-value path (mirror gate.* normalizeOptionalGateMode warnings)
• Tests: valid values, absent (default null), malformed value warning + ignore, all branches

References

• src/signals/focus-manifest.ts:124
• src/signals/focus-manifest.ts:283
• src/signals/focus-manifest.ts:421

Part of #1961.

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size: S · held for later release (gittensor:feature once activated)

[linear-code]

JSO-2274