Add Motion Prompt reference and stable showcase anchors

[changeroa]

Changes

• Add the requested Motion Prompt dictionary link to Motion, with source scope and verification limits.
• Keep 29CM's heading and four feed anchors present before JavaScript runs, so standalone examples have stable reading/navigation targets.
• Regenerate admitted material after the Motion index change.

Checks

• Domain, IA, lifecycle, and material validation passed.
• node scripts/check-showcase.mjs --work 29cm --richness error passed after the static fallback change.
• This supports the separate website change that exposes runnable examples for all 146 public documents.

consumer_reference: consumer-reference/agent-native/registry.json