fix(L4): preserve raw sessions skipped as recent(<2h) (#90)

compress_session.py Phase 4 builds to_del from both processed files
and every skipped file. Phase 1 marks files younger than 2h as
'recent(<2h)' (line 175) so their still-active writer is not
interrupted, but Phase 4 then deletes them anyway.

Filter the skipped-loop by reason so 'recent' files are preserved.
Processed files and other skip reasons (dup, compression error)
still proceed through deletion as before.

memory/L4_raw_sessions/compress_session.py

@@ -219,7 +219,8 @@ def batch_process(src, l4_dir=None, dry_run=True):
 
     # Phase 4: Delete raw files
     to_del = [rp for *_, rp in results]
-    for fname, _ in skipped:
+    for fname, reason in skipped:
+        if 'recent' in reason: continue  # active session still being written
         m = [f for f in raw_files if os.path.basename(f) == fname]
         if m: to_del.append(m[0])
     deleted = 0