docs(readme): rewrite the architecture section to match the tree

[LeadcodeDev]

Severity Medium, category coherence. Location: README.md:2034

Impact

Every structural claim in this block is false. Verified: there is no root src/ (ls src → No such file or directory, the tree is crates/*/src); there is no layout/ directory (ls crates/rustmotion-core/src/layout → No such file or directory — taffy replaced it); the Widget trait does not exist (grep -rn "Widget" crates/ returns exactly two hits, both comments, one of which is crates/rustmotion-core/src/traits/painter.rs:1: "Painter trait — replaces the old Widget::render"); the pipeline is box_tree → layout_pass → paint_pass, not "measure → layout → paint"; and the Component enum in crates/rustmotion-components/src/lib.rs:355-418 has 60 variants, not 51 (CLAUDE.md's "Composants disponibles (60)" is the correct count). The "CLI Reference" section (README.md:88-104) documents only rustmotion render and 9 of its flags, while crates/rustmotion/src/cli/mod.rs declares 11 subcommands (Render, Concat, Still, Captions, Validate, Batch, Schema, Info, Skills, Completions, plus nested) — validate, the gate CLAUDE.md makes mandatory before delivering any scenario, is entirely absent, as are --watch, --frames, --var, --props, --strict-anim. The branch HEAD (4d54504 fix(crates): ship the README with every published crate) adds readme = "../../README.md" to all four crate manifests, so this document becomes the front page of rustmotion, rustmotion-core, rustmotion-components and rustmotion-html on crates.io and docs.rs. A contributor following it looks for src/components/ and implements Widget.

Fix

Rewrite the Architecture block from the (accurate) one in crates/rustmotion/CLAUDE.md: the crates/ workspace layout, the box_tree → layout_pass → paint_pass pipeline, the Painter trait signature, and 60 components. Extend the CLI Reference to cover the other 10 subcommands, validate first. Add a test in the same family as crates/rustmotion/tests/skill_files_match_disk.rs asserting the README's component count equals Component's variant count, so this cannot silently drift again now that it is published metadata.

Evidence the audit read

├── components/              # 51 components (each implements Widget trait)
├── engine/
│   ├── render/              # Render pipeline (component, scene, background, transforms)
│   └── renderer.rs          # Skia drawing primitives
├── layout/                  # Flex/grid layout engines
├── traits/                  # Widget, Styled, Animatable, Timed, Container

Every component implements the `Widget` trait:

trait Widget {
    fn paint(&self, canvas: &Canvas, ctx: &PaintContext) -> Result<()>;
    fn measure(&self, constraints: &Constraints) -> (f32, f32);
    fn layout(&self, constraints: &Constraints) -> LayoutNode;

Based directly on the chantier branch.

Part of the September 2026 audit remediation chantier. Refs #220 (RM-02).

[LeadcodeDev]

Closed and reopened as a fresh pull request: GitHub registered this one as part of a stack, and a stacked pull request cannot be merged through either the GraphQL or the REST merge endpoint. The finding itself is unchanged.