habitable v0.2.0 — alpha hardening & reviewer handoff

Closes maintainer-only Phase 0: archive re-timestamping, vault key lifecycle,
packet-version contract + golden corpus, fuzz harness, public-TSA integration CI,
signed-provenance/SBOM release pipeline, custody-identity export fix + guard tests,
frozen threat-model baseline B1, and reviewer/pilot handoff docs. Still alpha.

docs(changelog): consolidate the v0.1.0 release notes

Fold the app, accessibility, mobile/PWA, relay-deploy, and preview work into a single v0.1.0 release (no tag had been cut yet), grouped under evidence core and app/accessibility/operations, with an honest Limitations note.

Threat-model baseline B1 (alpha) — frozen for external review; threat…

…-model.md sha256 809e0a43...fcb71f