Name the covering element in covered-interaction refusals #3488

Purpose

When an interaction is refused because the target is covered (reason: target_covered, node interactionBlocked: 'covered'), the geometric occlusion scan in packages/capture-kit/src/snapshot-occlusion.ts already knows which node covers the target (findCoveringNode returns it), but the annotation pass publishes only the boolean and the refusal carries nothing about the culprit. The agent must re-guess what to dismiss. Playwright's equivalent refusal names the intercepting element; agent-device should name the covering element too.

Required behavior

• The occlusion annotation pass carries a bounded description of the covering node on the covered node (e.g. coveredBy: { kind, label?, rect }), derived from the node findCoveringNode already found.
• Both covered-refusal producers surface it:
  • src/commands/interaction/runtime/target-visibility-stages.ts#buildCoveredInteractionError (press/fill/click/longpress/hover via ref, selector, and native-ref preflight, plus the selector-readiness diagnosis probe);
  • src/daemon/interaction/internal/find.ts#rejectCoveredFindMatch (find focus/type).
• The refusal error.details gains a typed coveredBy detail (bounded: presented role, trimmed/truncated label when the cover has one, rounded rect), and the hint names the covering element so the recovery is concrete.
• The cover's @ref is never advertised as actionable in the message, detail, or hint.
• When the cover identity is unknown — backend policy annotations such as annotateSnapshotNodesCoveredByPolicy (Android replacement surfaces) supply only a boolean — the refusal keeps today's shape: no coveredBy detail, no guessed culprit.
• Snapshot unchanged-comparison (src/commands/capture/runtime/snapshot-unchanged.ts) treats the new node field consistently with the other presentation annotations it compares.
• Update the owning help/docs recovery text that describes interaction refusals.

Observable completion conditions

• Unit tests through the public entry points:
  • annotateCoveredSnapshotNodes marks a covered node with the covering node's kind/label/rect; annotateSnapshotNodesCoveredByPolicy leaves coveredBy absent.
  • A runtime press of a covered ref/selector rejects with details.coveredBy naming the cover and a hint that names it; a policy-annotated covered node refuses without coveredBy.
  • Label truncation is bounded.
• Existing refusal-shape assertions (message, interactionBlocked, reason: target_covered) still pass.
• pnpm check:affected --run passes on the pushed head.

Part of the research sweep comparing agent-device refusals with Playwright's "intercepts pointer events" diagnostics.