feat(compose): template/skills library + compose (deploy slice 1)

[brettchien]

Slice 1 of the accepted agent-deployment ADR (#63): the compose seam — author a template/overlay/skills library and preview the composed {path → bytes} agent bundle. Studio-local, zero AWS / zero upstream: everything here is verifiable with cargo test + tsc/vite/vitest, no bundle-macos needed to know it's right.

What's here

crates/studio-compose — a new pure, dependency-light crate (serde + sha2, no async/AWS/fs):

• Template ⊕ Overlay + skills-by-reference → a deterministic Bundle ({path → Vec<u8>} + image tag).
• Precedence is last-writer-wins per path: template files < skills (under .claude/skills/<name>/…) < overlay files; image tag is overlay overriding template.
• Bundle::digest() — a length-prefixed sha256: content-address (the stable identity slice 2 / fleet-store ADR: Fleet Store & Control-Plane State Ownership #18 will key desired state on).
• Library aggregate + compose_named for the app/driver to look up by name; Bundle::preview() for a text-oriented, serde-friendly view.
• 17 unit tests covering precedence, skill resolution, error attribution (which layer referenced a missing skill), image-tag fallback, and digest stability / collision-resistance.

src-tauri — three commands (compose_library_get / compose_library_set / compose_preview) with compose.rs persisting the library as one JSON doc under the app config dir, mirroring config.rs (best-effort load, validated write).

console — a new Compose tab: edit the library as JSON, pick template + overlay, preview the composed bundle (image tag, digest, per-file content). Pure render helpers are unit-tested (compose.test.ts); the browser build disables the panel (no backend) like the Config tab.

Not here (later slices, per the ADR §3)

• Slice 2: ECS provision (push bundle → S3 state prefix + oabctl apply). Next.
• Slice 3: k8s driver. Slice 4: fleet-store (ADR: Fleet Store & Control-Plane State Ownership #18) wiring.

Verification

• cargo test -p studio-compose → 17 passed
• cargo check -p studio-compose clean. (The full cargo test --workspace OOM'd in my constrained build box while compiling oabctl's aws-sdk tree — an env limit, not a code issue; CI's build-test runner has the memory. src-tauri is its own workspace, compiled by bundle-macos.)
• cd console && npm run typecheck && npm test && npm run build → tsc clean, 65 vitest passed, vite build OK

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