Preserve OpenCode workspace identity in Navigator

[dbpolito]

Ticket

SKIPPED

Description

Preserve experimental Rift workspace identity throughout Navigator session lifecycle operations so newly created V2 sessions remain associated with their OpenCode workspace. Harden workspace discovery, placement validation, removal safety, and the Rift adapter boundary while retaining V1 and native Git-worktree compatibility.

Checklist

Session identity

• Carry Rift workspace IDs into new and existing-workspace V2 sessions
• Expose workspace identity in Navigator session and worktree results
• Validate project and location before prompt admission

Workspace safety

• Prefer identity-bearing Rift records and reject ambiguous registrations
• Match active sessions by workspace ID before directory fallback
• Restrict Rift operations to project-owned managed-root paths

Compatibility

• Keep V1, checkout, and native Git-worktree behavior directory-based
• Preserve existing output fields and avoid historical session migration
• Document Desktop and upstream experimental API limitations

Validation

• Verify that bun run compile succeeds
• Confirm that bun run typecheck reports no diagnostics
• Check that bun run test passes all 146 tests
• Verify that git diff --check reports no whitespace errors