feat(memsync): key memory sync by project fingerprint, not local path

[mja00]

Problem

claude-memsync keyed the sync repo by Claude's per-project directory name, which is the project's absolute path with separators replaced by dashes (-Users-me-code-foo). That name differs per machine, so a repo checked out at /Users/me/code/foo on one machine and /home/me/repos/foo on another was seen as two separate projects and their memories never merged. This was previously documented as the "same paths required" limitation.

Solution

Key the mirror by a machine-independent fingerprint instead of the local path:

• g-<hash> — normalized origin remote URL (all of git@github.com:Acme/app.git, https://github.com/acme/app, …/app.git collapse to one key)
• r-<hash> — git root-commit SHA, when the repo has no remote (with a shallow-clone guard)
• the dash-encoded path — fallback for non-git dirs (unchanged behavior; only merges across identical paths)

The Claude side stays keyed by its local dir name; a new internal/project package resolves each project's real path from the cwd Claude records in its session transcripts, derives the key, and keeps a per-PC ~/.claudesync/.state/index.json (gitignored) mapping localHash ↔ key. Reconcile/copy/remove and inbound propagation are now key-addressed. Projects synced from another machine but not yet opened locally materialize lazily on first open.

Migration: the first run after upgrading auto-migrates existing path-keyed mirror dirs to fingerprint keys, union-merging any that collapse to the same key via the existing claude-memmerge driver. Both machines must be upgraded for a project's divergent histories to converge. This is a pre-1.0 on-disk layout change → minor version bump.

Also: the foreground run daemon now logs startup and sync activity — previously it was silent, which read as a hang.

Verification

• go build ./... && go vet ./... && gofmt -l . && go test ./... all clean
• New unit tests: URL normalization, fingerprint tiering (remote/root/path incl. clone + shallow), cwd extraction, index round-trip, cross-path union reconcile, migration idempotency
• End-to-end with a bare-repo remote: two "machines" at different paths but the same repo converge to one g- key with a unioned MEMORY.md; a legacy path-keyed remote dir migrates and merges on upgrade