test(e2e): add worktree-remote and unreachable-remote scenarios (G2, G3)

• G2: an agent session runs inside a linked git worktree, the user commits and pushes the worktree's branch with a plain git push (the real pre-push hook syncs checkpoints — no explicit PushCheckpointRefs), and a fresh clone entire resumes the session. Exercises the worktree shadow-branch namespace and the shared common-dir push queue end to end.
• G3: entire doctor on a repo whose origin points at an unreachable (hermetic, missing local path) target completes without hanging or crashing and still reports its local session-health scan — pinning the degrade-to-local behavior.

Both are vogon-only (deterministic, free, part of the CI canary matrix). G2 reuses the resume-from-clone prompt phrasing verbatim so vogon's regex prompt parser needs no changes. Adds entire.DoctorCtx, a context-bounded doctor runner that returns output+error instead of failing the test, so G3 can surface a hang as a deadline.