fix: separate analyses dir so caching works with read-only recordings mount

The Docker web container mounts ./recordings as :ro, causing every cache
write to fail silently (PermissionError swallowed by bare except).

Fix: add --analyses-dir flag (default: <recordings>/analyses for local runs).
docker-compose.yml adds ./analyses:/analyses (writable) and passes
--analyses-dir /analyses to web.py. Cache write failures now print a
warning instead of being swallowed silently.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web.py

@@ -207,19 +207,18 @@ def analyze_flac(path: Path, window_samples: int = WINDOW_SAMPLES,
 # Analysis cache helpers
 # ---------------------------------------------------------------------------
 
-def _analysis_cache_path(base: Path, audio_path: Path) -> Path:
-    rel = audio_path.relative_to(base)
-    return base / 'analyses' / rel.parent / (rel.name + '.analysis.json')
+def _analysis_cache_path(analyses_base: Path, recordings_base: Path, audio_path: Path) -> Path:
+    rel = audio_path.relative_to(recordings_base)
+    return analyses_base / rel.parent / (rel.name + '.analysis.json')
 
 
-def prune_orphan_analyses(base: Path):
-    analyses_dir = base / 'analyses'
-    if not analyses_dir.exists():
+def prune_orphan_analyses(analyses_base: Path, recordings_base: Path):
+    if not analyses_base.exists():
         return
     removed = 0
-    for cache in analyses_dir.rglob('*.analysis.json'):
-        rel = cache.relative_to(analyses_dir)
-        audio_path = base / rel.parent / rel.name[:-len('.analysis.json')]
+    for cache in analyses_base.rglob('*.analysis.json'):
+        rel = cache.relative_to(analyses_base)
+        audio_path = recordings_base / rel.parent / rel.name[:-len('.analysis.json')]
         if not audio_path.exists():
             try:
                 cache.unlink()
@@ -283,6 +282,7 @@ def list_files(recordings_dir: str):
 
 class _Handler(BaseHTTPRequestHandler):
     recordings_dir: str = 'recordings'
+    analyses_dir:   str = 'recordings/analyses'
     threshold: float    = LOUD_THRESHOLD
     min_gap: float      = MIN_GAP_SECONDS
 
@@ -358,8 +358,9 @@ class _Handler(BaseHTTPRequestHandler):
         except Exception:
             pass
 
-        base = Path(self.recordings_dir).resolve()
-        cache_path = _analysis_cache_path(base, path)
+        recordings_base = Path(self.recordings_dir).resolve()
+        analyses_base   = Path(self.analyses_dir).resolve()
+        cache_path = _analysis_cache_path(analyses_base, recordings_base, path)
         try:
             cached = json.loads(cache_path.read_text('utf-8'))
             if cached.get('threshold') == threshold and cached.get('min_gap') == min_gap:
@@ -386,8 +387,8 @@ class _Handler(BaseHTTPRequestHandler):
             tmp = cache_path.with_suffix('.tmp')
             tmp.write_text(json.dumps({'threshold': threshold, 'min_gap': min_gap, 'result': result}), 'utf-8')
             os.replace(tmp, cache_path)
-        except Exception:
-            pass
+        except Exception as e:
+            print(f'Warning: could not write analysis cache {cache_path}: {e}', flush=True)
 
         self._send(200, json.dumps(result).encode('utf-8'), 'application/json')
 
@@ -512,7 +513,11 @@ class _Handler(BaseHTTPRequestHandler):
             return
 
         try:
-            _analysis_cache_path(Path(self.recordings_dir).resolve(), path).unlink()
+            _analysis_cache_path(
+                Path(self.analyses_dir).resolve(),
+                Path(self.recordings_dir).resolve(),
+                path,
+            ).unlink()
         except Exception:
             pass
 
@@ -1637,25 +1642,31 @@ def main():
                         help='Bind address (default: 0.0.0.0)')
     parser.add_argument('--threshold', type=float, default=LOUD_THRESHOLD,
                         help=f'RMS loudness threshold 0–1 (default: {LOUD_THRESHOLD})')
-    parser.add_argument('--min-gap',   type=float, default=MIN_GAP_SECONDS,
+    parser.add_argument('--min-gap',     type=float, default=MIN_GAP_SECONDS,
                         help=f'Seconds gap for merging loud sections (default: {MIN_GAP_SECONDS})')
+    parser.add_argument('--analyses-dir', default=None,
+                        help='Directory for analysis cache files (default: <recordings-dir>/analyses)')
     args = parser.parse_args()
 
-    rec_dir = Path(args.dir)
-    if not rec_dir.exists():
-        print(f"Warning: recordings directory '{args.dir}' does not exist yet.")
+    rec_dir      = Path(args.dir).resolve()
+    analyses_dir = Path(args.analyses_dir).resolve() if args.analyses_dir else rec_dir / 'analyses'
 
-    prune_orphan_analyses(rec_dir.resolve())
+    if not rec_dir.exists():
+        print(f"Warning: recordings directory '{rec_dir}' does not exist yet.")
+
+    prune_orphan_analyses(analyses_dir, rec_dir)
 
     class Handler(_Handler):
-        recordings_dir = str(rec_dir.resolve())
+        recordings_dir = str(rec_dir)
+        analyses_dir   = str(analyses_dir)
         threshold      = args.threshold
         min_gap        = args.min_gap
 
     server = ThreadingHTTPServer((args.host, args.port), Handler)
 
     print(f"ISR Web running → http://{args.host}:{args.port}/")
-    print(f"Recordings dir  → {rec_dir.resolve()}")
+    print(f"Recordings dir  → {rec_dir}")
+    print(f"Analyses dir    → {analyses_dir}")
     print(f"Loud threshold  → {args.threshold}")
     if not NUMPY_AVAILABLE:
         print("Note: numpy not installed — WAV RMS uses pure Python (slower); FLAC analysis unavailable")