docs(M003): reassess roadmap after S01

.gsd/milestones/M003/slices/S01/S01-ASSESSMENT.md

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+# S01 Post-Slice Assessment
+
+**Verdict: Roadmap is fine. No changes needed.**
+
+S01 delivered exactly what was planned — 6 lifecycle functions, auto.ts integration, 21-assertion test suite. No deviations, no new risks surfaced, no assumption changes.
+
+## Success Criteria Coverage
+
+All 6 success criteria have remaining owning slices. No gaps.
+
+## Boundary Contracts
+
+The boundary map remains accurate. S01's produced APIs (`createAutoWorktree`, `teardownAutoWorktree`, `isInAutoWorktree`, `getAutoWorktreePath`, `enterAutoWorktree`, `getAutoWorktreeOriginalBase`) match what was planned. S02–S07 consume these as specified.
+
+## Requirement Coverage
+
+R029 and R039 advanced as expected. No requirements invalidated, re-scoped, or newly surfaced. All 13 active requirements remain mapped to their planned slices. Coverage is sound.
+
+## Risk Retirement
+
+The three key risks identified in the proof strategy were all addressed by S01:
+- `process.chdir` coherence — proven via atomic chdir + state update pattern
+- `.gsd/` inheritance — planning files verified accessible in worktree
+- State machine re-entry — resume path re-enters worktree correctly
+
+No residual risk carries forward unexpectedly.