feat(compose): add atelier (bespoke) composition mode + doctrine

Introduce a hand-authored, project-local Remotion render path that bypasses
the cut-schema and the stock scene-type registry, for hero/bespoke videos
that must look distinct from one another.

- video_compose: composition_mode="atelier" (or renderer_family="bespoke")
  routes to _render_via_atelier, which renders a project-local entry under
  remotion-composer/projects/<slug>/ with an optional per-project public_dir
  (skips copying the bloated shared public/). No cut-schema, no stock registry.
- skills/meta/bespoke-composition.md: routing skill — art direction
  (visual-style) -> motion principles (Disney 12) -> engine mechanics
  (remotion-best-practices + stock components read only as a mechanics codex)
  -> atelier render. Doctrine: reuse engine knowledge, never creative components.
- AGENT_GUIDE: "Composition Authoring Mode" (templated vs atelier); default
  atelier for hero work; scene-type catalog reframed as a mechanics codex.
- animation-runtime-selector + INDEX: authoring-mode-first pointers.
- base_tool.run_command: decode subprocess output as UTF-8/replace (Windows
  cp1252 crashed the reader thread on Remotion's Unicode progress output).
- .gitignore: remotion-composer/projects/ (throwaway bespoke compositions).

AGENT_GUIDE.md

@@ -130,6 +130,15 @@ Exception: if only one runtime is available on the machine, the agent proceeds w
 
 This rule applies to every pipeline that invokes `video_compose` — not just Wave 1. A pipeline's director skill may recommend a runtime, but that recommendation is input to the conversation with the user, not a decision.
 
+### Composition Authoring Mode — Templated vs Atelier
+
+Orthogonal to *runtime* is *authoring mode*: **how** the composition is built. Present it as its own proposal decision and log it in `decision_log` (`category: "composition_mode"`).
+
+- **Templated** — assemble the stock `cut.type` scene-types (`text_card`, `stat_card`, `bar_chart`, …) into the `Explainer`/`CinematicRenderer` compositions. Fast, cheap, reliable — and the reason most videos look alike. Right for batch output, localization variants, quick drafts, and low-stakes internal clips.
+- **Atelier** — **hand-author the composition from scratch**: bespoke scenes, a one-off theme, and motion written for this piece, rendered via `composition_mode: "atelier"` (see `video_compose` → `_render_via_atelier`). No reusable creative components; a fresh visual language every time.
+
+**Default to atelier for hero work** — marketing, launches, brand pieces, any single-deliverable explainer that must impress. The deciding rule: *reuse engine knowledge, never creative components.* In atelier mode the stock scene-type catalog, `hyperframes-registry` blocks, fixtures, and finished components are **off-limits** — they are frozen looks that reintroduce sameness. Before building, route through **`skills/meta/bespoke-composition.md`**, which sequences: art direction (`visual-style`) → motion principles (Disney 12 via `framer-motion`/`lottie-bodymovin`) → engine mechanics (`remotion-best-practices` + the stock components read *only as a mechanics codex*) → render via the atelier path. Close with a **distinctness review**: *could this be any other product's video? does it reuse a look I've made before?* — the inverse of "does it match the reference." Atelier costs more tokens and iteration than templated; say so at proposal so the user opts in knowingly.
+
 ### Escalate Blockers Explicitly
 
 When a blocker occurs, the agent must surface it immediately using this structure:
@@ -396,6 +405,8 @@ For these requests:
 See `remotion-composer/SCENE_TYPES.md` for the authoritative list and their cut schemas. Current scene types usable via `cut.type`:
 `text_card`, `stat_card`, `callout`, `comparison`, `hero_title`, `terminal_scene`, `anime_scene`, `bar_chart`, `line_chart`, `pie_chart`, `kpi_grid`, `progress_bar`. Overlay types include `section_title`, `stat_reveal`, `hero_title`, `provider_chip`.
 
+These stock scene-types are the **templated** path — fast and reliable, but they are why videos look alike. For **hero work, prefer atelier mode** (hand-authored composition) over this catalog; read those types as a *mechanics codex*, not a menu to assemble. See "Composition Authoring Mode" above and `skills/meta/bespoke-composition.md`.
+
 **When Remotion is NOT available** and `render_runtime="remotion"` was NOT locked, `video_compose` may use FFmpeg Ken Burns motion on still images. This still works but produces less engaging visuals. Mention this tradeoff in the proposal. When `render_runtime="remotion"` IS locked and Remotion is unavailable, that's a blocker — escalate, don't silently swap.
 
 When `render_runtime="hyperframes"` is locked and HyperFrames is unavailable (Node < 22, missing `ffmpeg`/`npx`, or `hyperframes doctor` reports issues), that's also a blocker. Do not substitute Remotion or FFmpeg without user approval + a logged `render_runtime_selection` decision.