style(rmi-backend): complete lint cleanup — 1175→0 ruff errors

- Fix 71 invalid-syntax files (class-body newline-broken assignments)
- Add from/None chain to 307 B904 raise-without-from sites
- Add B008 ignore to ruff.toml (already in pyproject.toml)
- Noqa F401 on __init__.py re-exports (137 sites)
- Noqa E402 on deferred imports (63 sites)
- Bulk-add stdlib/FastAPI/project imports for F821 (127 sites)
- Replace ×→x, –→-, …→... in docstrings (4093 chars)
- Manual refactor of 5 SIM103/SIM116 patterns

Tests: 791 passed (66 deselected due to pre-existing Redis issues in test_rag.py)
Co-authored-by: opencode <opencode@rugmunch.io>

scripts/export_openapi.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 """Export the auto-generated OpenAPI schema from the FastAPI app.
 
-Per T14 (G09 FIX) — never hand-maintain openapi.yaml/openapi.json. Always
+Per T14 (G09 FIX) - never hand-maintain openapi.yaml/openapi.json. Always
 auto-generate from the live FastAPI routes. SDK generation (Python, TS)
 and MCP manifests depend on this being a faithful snapshot of the code.
 
@@ -80,7 +80,7 @@ def main() -> int:
             print(
                 f"FAIL: OpenAPI has only {path_count} paths "
                 f"(minimum {args.min_paths}). "
-                f"Factory imports are likely broken — check that all "
+                f"Factory imports are likely broken - check that all "
                 f"routers in app/api/v1/ and app/domain/* import cleanly.",
                 file=sys.stderr,
             )