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/VERDICT.md

@@ -0,0 +1,20 @@
+# Verdict: hook-install-process
+
+## Status: PASS
+**Completion Date**: 2026-06-15
+
+## Summary
+Added pre-commit hook installation to onboarding and upgrade processes. Three files changed: onboarding prompt, upgrade.sh, and install.sh. All 200 tests pass, shell syntax checks pass.
+
+## Findings
+- Onboarding prompt now includes Step 2c for git hook installation
+- upgrade.sh installs hook with symlink detection and conflict warning
+- install.sh mentions hook setup in post-install steps
+- Pre-commit enforcement working correctly (blocked a commit without a task)
+
+## Remaining Issues
+- upgrade.sh doesn't verify python3 is available (low severity)
+- Pre-commit hook assumes `.git/hooks/` path (doesn't handle bare repos or worktrees)
+
+## Score
++10