feat: gemini image analyzer (auto-detect role/vibe/treatment on upload)

[cuio]

Summary

Closes Milestone D from #25. Every image upload now fires a fire-and-forget Gemini Flash analysis that tags the manifest entry with role, mood vibe, a recommended image-scene suggestedTreatment, and a 1-10 retentionStrengthAtAttachment estimate. The visual director consumes those fields as soft priors, so the very first render has intentional visual logic instead of defaulting to editorial-bleed across every scene.

• packages/core/src/images/analyzer.ts — Gemini Flash + inlineData (base64 webp) for sub-2s latency; pure normalizeAnalysis defends against out-of-range scores, unknown enums, and missing fields.
• packages/core/src/images/manifest.ts — ImageEntry gains vibe, suggestedTreatment, retentionStrengthAtAttachment, analysisStatus, analysisError, analyzedAt, analysisRationale. All optional, so old manifests load unchanged.
• packages/core/src/studio-api/routes/images.ts — Upload patches analysisStatus: pending synchronously, fires analysis off-cycle, writes result back. New POST /images/:id/analyze re-runs on demand.
• packages/core/src/script/visualDirector.ts — Catalog labels new fields as (analyzer prior) so the LLM treats them as advisory; new constraint feat(script): cinematography agents + hook layering + ssr cache fix #10 + retention-strength guidance for hook scenes.
• packages/studio/src/components/sidebar/ImagesTab.tsx — Row chip shows analyzing… / R7 (color-coded retention) / analysis failed. Editor gains an Analyzer panel with vibe / treatment prior / score / rationale, plus a re-analyze button that optimistically flips state.

Cost

Logged under script.images.analyze with kind: "gemini". ~$0.001 per image at gemini-2.5-flash rates.

Tests

15 new analyzer tests (clamping, role coercion, treatment normalization, char-clipping, default-treatment helper). Full suite green: 745 core + 281 studio passing.

Failure modes

• GEMINI_API_KEY missing → entry flips to analysisStatus: "failed" with a "configure it in Settings" reason. Upload still succeeds.
• Network error / model decline → same fail-soft path; user-typed role / description / tags are preserved and never overwritten.
• File missing on disk (raced delete) → analyzer returns the failed entry rather than throwing.

Test plan

• Upload a fresh image to a project that has GEMINI_API_KEY set → row chip shows analyzing… for 1-2s then flips to R<n> color-coded.
• Inspect the entry → analyzer panel shows vibe + treatment prior + rationale.
• Re-render the project → visual director's catalog now includes the prior; rationales reference it.
• Click ↻ re-analyze on an existing image → chip flips to analyzing… then refreshes with new values.
• Remove GEMINI_API_KEY and upload a new image → chip shows analysis failed with the reason on hover; upload still succeeds.

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