Route project media generation through Summer Studio

[TimofeySukh]

Summary

• add a Studio-only media generation boundary to the core Summer workflow and asset router
• prohibit Python, GDScript, shell, native chat, and external-generator fallbacks for authored project media
• require durable Summer asset imports and stop with a Studio dashboard handoff when generation tools are unavailable
• add the same invariant to the MCP agent playbook and cover it with a regression test

Verification

• npm test — 47 test files, 433 tests passed
• npm run build
• git diff --check origin/main...HEAD

Scope

Prompt-only behavior change. No generator implementation, tool permissions, or runtime enforcement changed.

[TimofeySukh]

Rebased onto v3.0.0 (main @ 11cc6a3) and force-pushed to codex/studio-only-media-prompts.

What moved where

• The three SKILL.md edits auto-merged via rename detection into the v3 library layout: library/skills/asset-strategy/SKILL.md, library/skills/music-track/SKILL.md, library/skills/using-summer/SKILL.md — content is byte-identical to the original PR hunks (Studio-only media boundary sections + fallback/anti-pattern rewording).
• The playbook safeDefaults rule from src/mcp/tools/project-tools.ts (deleted inline playbook in v3) is ported verbatim to src/core/capabilities/agent-playbook.ts — same rule wording, same position (after the GDScript-default rule).
• The regression test stayed in src/mcp/tools/project-tools.test.ts (the playbook tool test file in v3 too), asserting the exact boundary phrases from the playbook output.
• npm run generate:registry rerun; regenerated registry/generated/index.json content hashes committed as a separate chore(registry) commit per repo convention.

Exclusions: none — every change in the original commit was transplanted.

Verification

• npx tsc --noEmit — pass
• npx vitest run — 1449 passed, 10 skipped, 0 failed (102 files)
• npm run validate:library — 208 resources valid, 0 errors (pre-existing reciprocity warnings unchanged)
• npm run eval:routing -- --check (CI parity gate) — PASS, no regression vs committed baseline

[TimofeySukh]

Closed as included in MCP review stack #27 (review/tim/mcp-2026-09-11) — combined vitest 1480 passed, validate:library clean, registry regenerated, CI green. Review happens on #27.