migration: close candidate maintenance audit

app/tools/README.md

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+# Candidate tools
+
+Run these commands from `webapp/app/`. The tools are separated by responsibility so a
+maintenance command cannot be mistaken for a historical migration rewrite.
+
+## Normal maintenance
+
+- `python tools/verify_baseline.py`: candidate unit tests, registry checks, every frontend
+  JavaScript syntax check, Git whitespace check, and read-only SQLite integrity check.
+- `python tools/verify_baseline.py --e2e`: the same checks plus Playwright. The verifier owns
+  the local static-server lifecycle so the command exits cleanly on Windows.
+- `python tools/build_api_registry.py [--check]`: generate or verify
+  `config/api.config.json` from `backend/application.py`.
+- `python tools/build_architecture_inventory.py [--check]`: generate or verify
+  `config/architecture-inventory.json` from the candidate source tree.
+
+## Acceptance and differential checks
+
+- `run_preservation_runtime.py`: start an isolated original or candidate runtime with an
+  explicitly selected data directory and port.
+- `compare_preservation_apis.py`: compare authenticated responses from two isolated runtimes.
+- `compare_preservation_databases.py`: compare schema and selected table contents from two
+  SQLite copies.
+
+These tools require explicit paths and do not select the production database automatically.
+
+## Migration-only tools
+
+- `build_preservation_manifest.py`: builds an exact-copy manifest for a specified source and
+  target. `--output` is mandatory so committed historical evidence is not overwritten.
+- `move_class_methods.py`: mechanically moves named class methods between explicit files.
+- `split_frontend_runtime.py`: reproduces the one-time Slice 10 split. It refuses to write
+  unless `--apply` is supplied and is not a normal maintenance command.
+
+The migration-only tools are retained for audit and reproducibility. They are not part of
+application startup, normal testing, or future feature development.