Deepen Bombadil scenario exploration

[0thernet]

Summary

• add serial scenario matrices, exact viewport configuration, privacy-bounded exploration summaries, and fail-closed anti-vacuity policies
• add supported resource-growth properties and exclude destructive generic click intents
• document bounded liveness, replay, trace sensitivity, responsive versus interaction evidence, and the v0.7.6 release boundary

Evidence

• source and diff checks are clean on the exact branch
• local frozen install, complete gate, package smoke, and browser campaigns remain deliberately unstarted under the active shared-resource hold
• hosted Required CI is the first executable validation and this PR remains draft until exact-head gates pass