M3: Capture Tool (litmus-capture) (litmus-lizo)

New workspace crate crates/litmus-capture/. CLI binary with: capture, capture-all, upload, manifest commands. Kitty provider module. Uses cage for headless Wayland, grim for screenshots, FiraCode font, 80x24 geometry. WebP output to staging dir.

Summary of Changes

Created crates/litmus-capture/ — a new workspace crate (native binary, excluded from wasm build).

Modules:

• error.rs — CaptureError enum for typed errors
• providers/mod.rs — ProviderCapture trait + TermGeometry struct + provider registry
• providers/kitty.rs — KittyProvider: generates kitty.conf with theme colors + FiraCode/80×24/no-decorations settings; builds launch args
• capture.rs — core capture logic: fixture setup, cage+kitty orchestration via wrapper script, sentinel-file completion detection, grim screenshot, PNG→WebP conversion, sha256 checksum
• manifest.rs — builds ScreenshotManifest by scanning staging/{provider}/{theme}/{fixture}.webp; CoverageReport for CI validation
• main.rs — CLI with clap: capture, capture-all, manifest build, manifest check subcommands

Key design:

• Fixture lifecycle: setup.sh → kitty+command.sh in cage → sentinel file detection → grim screenshot → PNG→WebP
• wrapper.sh runs inside cage’s Wayland session; both kitty and grim connect to cage’s compositor
• Fixed geometry: 80×24 cols/rows, FiraCode 12pt
• 16 unit tests pass; 83 total workspace tests pass