docs: describe the six capabilities shipped since the differential was re-scored

[LeadcodeDev]

Six features landed in #168–#178 that neither CLAUDE.md nor any rule mentions. For a tool whose scenarios are generated, a capability the rules do not describe may as well not exist — issue #165 was this exact failure one level down, where the distribution channel silently dropped 17 rules.

What is now documented

Two new rules

• templates-and-iteration.md — components / for-each / use. The largest new vocabulary, aimed at the failure mode the original audit called dominant: a generator duplicating a repeated structure by hand.
• motion-path.md — the effect, its SVG path syntax (the same one shape: {"type":"path"} already uses), and why the coordinates are deltas from the layout position rather than absolute.

Two extended

• geometry-safety.md gains text-autofit as a fourth viewport control alongside white-space, auto_scroll and overflow — including the floor, and the fact that a violation is still reported when shrinking is not enough. It also says plainly that only text and gradient_text implement it, so declaring it on a caption is inert.
• timeline-sequencing.md gains what style.transition actually smooths: the four interpolated properties, and the three distinct reasons a property snaps instead — layout, discrete, unsupported-paint — since validate now names them. With the practical consequence: animate transform, not width.

CLAUDE.md picks up the same, plus --frames / rustmotion concat, --hardware-acceleration, and the --fix refusal rules.

Running the examples found a real trap

The docs' own examples were executed, not just written. One failed:

Warning: Unresolved variable reference '$accent' after substitution
Error: color '$accent' is not a recognized CSS color

A for-each item that omits a field, forwarded through a use's props, passes the literal $name through instead of falling back to the component's default. A params default applies when props omits the key — not when it forwards an unresolved binding.

Nothing is silent about it: an unresolved-variable warning fires, then the consumer rejects the value. But it is the natural way to write "optional field with a default", so it now has its own section in the rule, with the working form. The example is corrected and validates.

This is the argument for running documentation rather than reviewing it.

The distribution pipe works

The two new rules ship without touching skills.rs:

$ rustmotion skills install
Installed 51 file(s) to .claude/skills/rustmotion/   (was 49)

49 rules on disk, 49 embedded, exhaustiveness test green. That is PR #168's build script doing exactly what it was written for — the fix for #165 proving itself on the first real addition since.

Verification

• cargo test --workspace: 30 targets, 0 failures
• cargo fmt --all --check: clean
• Examples: 7 of 8 validate (the eighth is examples/ferriskey-presentation.json does not pass rustmotion validate (pre-existing on main) #157, pre-existing)
• The scenario combining every documented form — components + for-each + use + motion_path — validates under --strict-anim

Still undocumented

The spring's duration / rest_threshold (#168) and rustmotion info's Media assets section (#178) are mentioned nowhere yet. Both are CLI-facing rather than scenario vocabulary, so they matter less to a generator, but they are gaps.