fix Cursor slug scan hang

[Guiraud]

Summary by cubic

Fixes a hang when scanning Cursor project slugs by bounding slug-to-cwd decoding and short-circuiting cwd resolution via repo.json. Also adds cwd-scoped parsing so we only scan relevant Cursor projects, keeping lookups under 100ms.

• Bug Fixes

  • parseCursorSessions accepts { cwd }, reads repo.json first, and filters projects before scanning transcripts.
  • Adds bounded fallback in cwdFromSlug for long/Volumes slugs and preserves Windows drive behavior.
  • Preserves exact cwd when a long slug matches without repo.json, avoiding exponential decoding.

• Refactors

  • cursor adapter marked supportsCwdLookup; buildIndex/getSessionsByCwd pass cwd only to supported adapters and filter cached results.
  • Cwd-scoped parses are not written to the global index.

^{Written for commit 50ac839. Summary will update on new commits.}