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/BUG_REPORT.md

@@ -0,0 +1,10 @@
+# Bug Report: hook-install-process
+
+## Summary
+No code bugs found. Process issue: the task was created after implementation was complete, which is a violation of the framework's own process. Otherwise, the changes are minimal and correct.
+
+## Bugs Found
+None.
+
+## Score
++10