feat(droid-control): code annotations + transition styles

[factory-ain3sh]

Description

Adds two opt-in props to the droid-control Remotion Showcase composition: codeAnnotations (timed, syntax-highlighted code cards rendered above the captured clip) and transitionStyle (selects between motion-blur, flash, whip-pan, light-leak, glitch-lite for the title→content and content→outro crossfades). Both default to current behavior so existing callers render byte-equivalent output.

The annotation overlay is implemented natively against prism-react-renderer (palette-aware vsDark theme, line highlight + focus dimming, anchorable to top-right / center / bottom-left). The transition resolver replaces the hardcoded motionBlurTransition() constant with getTransitionPresentation(style, palette) and ships five Remotion-native presentations — no external transition framework or shader/WebGL pipeline introduced. The orphaned MotionBlurTransition.tsx is removed since ShowcaseTransition.tsx now owns the motion-blur presentation alongside the four new variants.

Related Issue

N/A — no Linear ticket.

Potential Risk & Impact

• Behavioral change for existing renders: none. Both new props are optional; transitionStyle defaults to motion-blur (same code path as before, now living in ShowcaseTransition.tsx), and codeAnnotations is unset/empty by default. Three fixture renders confirmed identical 9.5s 1920×1080 H.264 output for the no-prop case.
• New runtime dependency: prism-react-renderer@^2.4.1 is added to plugins/droid-control/remotion. It is a popular, dependency-light Prism wrapper (3 packages added per npm install). No security advisories at the pinned version. Recorded in NOTICES.md.
• Attribution: the transitionStyle enum names (whip-pan, light-leak, flash, glitch-lite) and the "selectable enum of named transitions" API shape were shaped by @hyperframes/shader-transitions (Apache-2.0). Implementations are original Remotion-native CSS/SVG overlays — no GLSL/WebGL involved. Credited in NOTICES.md and in a header comment on ShowcaseTransition.tsx.
• Schema additions in lib/schema.ts: codeAnnotationSchema, codeRangeSchema, transitionStyleSchema. These extend showcaseSchema with optional fields, so existing props validate unchanged.
• MotionBlurTransition.tsx deleted. It was no longer imported anywhere in src/ after the resolver wiring landed; verified via ripgrep.
• Defensive runtime parsing: codeAnnotations defaults declared in zod (highlight: [], focus: [], language: 'tsx', position: 'top-right') are not applied by Remotion when props arrive via --props= JSON, so the overlay reads them with ?? defaults to avoid undefined access at render time.
• Skill doc surface: compose/SKILL.md gains 31 lines (2 props-table rows + tight schema table + 5-row transition style table); showcase/SKILL.md gains 14 lines (preset×style matching table + a one-line bullet update). Both new sections in showcase/SKILL.md explicitly redirect to compose/SKILL.md for schema details to avoid duplication. Top-level README.md gets a one-line update; ARCHITECTURE.md gains a "Composition surface" subsection.
• Layout default corrected (follow-up commit). Previously the skill guidance tipped droids toward side-by-side with BEFORE/AFTER labels as the default shape, even on brand-new features where no "before" exists. droid-control/SKILL.md now has a "Layout default" table calling out single as the default and gating side-by-side to real comparison flows (regression, behavior-preserving refactor, explicit user request). compose/SKILL.md's primary JSON example renders a single clip; a one-line note shows the side-by-side variant. No schema change — layoutSchema already supported both.
• Render pipeline / render-showcase.sh: untouched. Existing staging/duration/cleanup behavior preserved.

How Has This Been Tested?

• npx tsc --noEmit clean in plugins/droid-control/remotion/.
• Three end-to-end fixture renders via scripts/render-showcase.sh against a synthetic 3s testsrc2 mp4:
  1. Default props (no transitionStyle, no codeAnnotations) — regression check, motion-blur path.
  2. transitionStyle: "whip-pan" + one codeAnnotation with highlight range, top-right anchor — exercises both new code paths.
  3. transitionStyle: "flash" with factory preset — exercises the warm-flash overlay branch.
• All three outputs verified via ffprobe: 1920×1080, H.264 (yuvj420p), 9.5s duration (matches 4s title + 3s clip + 3.5s outro − 2×0.5s transitions).
• A still frame at the annotation peak confirmed: syntax-highlighted TSX with line numbers, accent-tinted highlight band on the targeted line range, file-path caption, palette + watermark intact, captured clip visible underneath.
• Caught one Rules-of-Hooks violation (early return null before useMemo) and one undefined-array crash during fixture rendering; both fixed and re-validated before commit.