v1.20.0 — root-named project slugs + ADR relations at registration

• #294 root-named project slugs (PR #295): Project slugs are now named after the project ROOT (.git dominant, UM_PROJECT_MARKERS respected). Existing subdir-named layers are NOT migrated and age out. The only operator action is the normal plugin/install-cli refresh. um-preview from a subdirectory now needs --project. Success hook.log lines carry project=<slug>. Recall reads the same slug capture writes (session-start adopts the guard). Live-verified post-merge from fresh sessions in a repo subdirectory and in a .git-less marker project: session-start and session-end both logged the root slug; no subdir-named layer minted.
• #271 ADR relations at registration (PR #293): /adr sync now carries supersedes / superseded_by from the ADR's frontmatter into the registered point (label-only — status still derives from the file's own status:; omitted when empty; follows the file on every re-sync).
• Zero server runtime changes; the image is rebuilt for the version stamp only.

Deploy notes: the slug change lives in the hooks and CLI, not the server — every consumer machine keeps the old cwd-basename derivation until it refreshes the plugin (claude plugin marketplace update universal-memory + reinstall) and the installed CLI (installer/install-cli.sh). Until then, old-derivation junk layers re-firing LAYERS-STALE is the alert working. The install-cli refresh also clears the #271 installed-copy residual (create-adr lib).

Artifact verification: ghcr.io/goldenwo/universal-memory-server:1.20.0 pulled and booted per-arch (amd64 + arm64 under QEMU) against a throwaway qdrant with the real provider key — /health 200 on both, mem0ai/oss resolves on both (node v22.23.2).