use-action-form + action-form-core are dead code on Mars (zero call sites)

Flagged by coder-pluto-cc after PLUTO-535 found the same drift. Measured on mars: useActionForm has ZERO call sites in src/ - the only three hits are its own definition, its own usage comment, and a cross-reference comment in action-form-core.ts. action-form-core.ts is imported by use-action-form.ts and nothing else (feedback-core.ts mentions it only in a comment), so both files are dead. Cause is the same as pluto's: b3efa4d moved friction capture into the toast provider (renderer-owns-capture, mechanism=toast), which replaced the per-call-site path across ~115 sites without touching them, and use-action-form dropped onFriction at the same time - leaving the hook with nothing to do and no caller. NOT vacuous-lint: scripts/lint-no-silent-failure.mjs accepts any of useActionForm|checkRequired|addToast|useToast|ErrorBanner|aria-invalid|setError, so the surviving alternates still carry the check and removing the hook does not blind it - verified before filing. Decision needed, NOT a unilateral delete: action-form-core.ts is a VENDORED copy shared with pluto/venus, and editing or deleting a vendored file forks it and un-fixes its upstream history. Fleet call per coder-pluto-cc, who left pluto's copy byte-for-byte with a header status note for the same reason.