Fix pre-existing issues and update README for v2.0

- Fix _infer_state_from_artifacts: SPEC-only maps to research (was bug_find)
- Fix cmd_validate_folder: corrupted .state files now error instead of silent fallback
- Fix upgrade.sh: remove || true, add python3 check, use git rev-parse --git-dir
- Update README.md with --project flag, --can-edit modes, --upgrade, enforcement layers
- Add 6 new tests for inference and validation fixes
- Complete hook-install-process and readme-upgrade-docs tasks

tasks/hook-install-process/DOC_REVIEW.md

@@ -0,0 +1,17 @@
+# Documentation Review: hook-install-process
+
+## Summary
+Review of documentation for hook installation changes.
+
+## Documentation Plan Compliance
+- [x] prompts/onboarding.md — Step 2c added with hook installation
+- [x] scripts/upgrade.sh — Hook installation logic with error handling
+- [x] scripts/install.sh — Post-install steps mention hook setup
+- [x] AGENTS.md — Repository layout includes git-hooks/ directory
+- [x] contracts/harness-integration.md — Pre-commit hook section with installation instructions
+
+## Issues Found
+None — documentation is complete and consistent.
+
+## Score
++5