docs: the rig guarantees the seams, and the composing is the consumer's

[firejune]

Closes #445. bun run selftest 568 PASS / 0 FAIL / 0 SKIP / 0 HOLE, exit 0 — unchanged, as a text-only change should leave it.

The caption

Scene direction of this kind is authorable on plain Spine 4.3

The rig guarantees the seams — idle loops while gaze and turn return to rest, so the hand-offs meet at 0 differing pixels — and the composing is the consumer's.

⭐ This is an upgrade rather than a hedge, and the reason is measurability. "Scene direction" cannot be measured. The seam can, and films/three-scene already measured it: "That is a property of the rig rather than of the assembler… Step 7 measures exactly that and gets 0 differing pixels." The film proved the object-side claim in its own body; only the wrapper mislabelled it.

<code> rather than backticks, following the dominant form in the file's other two captions — a caption inside raw <em> is not a place to gamble on inline markdown.

The bone name

docs/FACE.md illustrated a fix as "splitting a bone into a stack (headroll_idle under headroll_scene)".

⚠️ A previous pass called this a socket name and therefore ours. That was wrong, and reading the line is what corrected it — it is not a socket, it is a hypothetical bone in prose, and the sentence containing it says outright that "both are runtime or rig decisions the motion spec cannot express". So the thing being named is consumer-side.

headroll_layer, because the same sentence already says "on the layered track". The name now says what the sentence says, and nothing is borrowed.

Two sites the card lists, deliberately unchanged

• films/three-scene/ keeps its name. A demo is the one place a scene belongs — "there we are the consumer" — and the name is honest. Renaming it would make the tree less accurate, not more.
• assets/rigc-scene.gif keeps its name. README.md links it by a raw githubusercontent URL on main, so renaming breaks that link for every cached and forked copy of a 3.11 MiB asset. A filename carries the link; the caption carries the claim. The card says a rename is not required by the rule, and it is not.

Two further sites left alone on the card's own instruction — checked, not assumed

docs/FACE.md:841 ("scene work exercises a renderer where game-part work does not") and :903 ("a scene-direction budget"). Both are about the art's fidelity and the renderer, not about who composes.

🔁 A previous application of this rule listed four violations and three fell away on inspection. Sweep the claim, not the word — a grep-and-replace here is the over-application that makes a good rule annoying and then ignored.