fix: require text-capable local reviewer models

[atomantic]

Summary

• require the shared tool-free local selection policy to expose a text-capable model
• reject embedding-only and unknown-capability models in both UI and server preflight validation
• keep the existing no-tools and local-provider boundary fail-closed

Validation

• client focused tests: 295 passed
• server focused scheduler/security tests: 408 passed
• client lint and production build passed
• full server suite: 36,899 passed; unrelated image/sprite suites timed out under full-suite load

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