Interaction-posture build warnings + posture reference docs

Emit the interaction-posture build warning and document the posture in the reference + composability docs.

Tracking started Jun 9 — check back for trends.

Relationships

main current done

A genuinely-interactive guest in a linked tile emits a build warning (still renders presentationally; informative, not fatal).
card/bento reference + composability docs document the posture (presentational-by-default, href-wins demotion, cover backdrop) and the build warning.

SPEC-084 validation philosophy. SPEC-090 §2 + Docs.

Completed: 2026-06-09

Branch: claude/spec-090-media-guest-posture

Build warning: warnInteractiveGuestInLink in packages/transform/src/engine.ts — "interactive guest <g> in a linked <container> — its controls are inert under the whole-tile link. Drop href or the interactivity." Informative, not fatal; the guest still renders presentationally. Deduped once per container:guest.
Docs:
- site/content/extend/rune-authoring/composability.md — new "Media-guest interaction posture" section (presentational-by-default + the interactive capability, href-wins demotion, cover backdrop, content-controls-stay-interactive, the build warning, full-bleed-widgets out of scope).
- site/content/runes/card.md — "Media guests in a linked card" subsection under Whole-card links.
- site/content/runes/marketing/bento.md — posture note in the Media zones section.
- All cross-linked to the composability contract anchor.

Follows SPEC-084's validation philosophy (build warnings, open-world — a rune participates by declaring interactive).