fork: MIT LICENSE + foundation patches (atomicity, locking, safety)

This is the initial fork commit for agent-admin/memoria, a production
hardening of coleam00/claude-memory-compiler. It addresses all four P0
findings from the bug audit (atomic state writes, file locking on
daily log appends, subprocess detachment, path-traversal guard) plus
several P1s (aliased wikilinks, timezone wiring, staleness-based
compile trigger, SDK retry with backoff, file-handle context manager).

File-level changes:

- LICENSE — MIT (fork is self-declared FOSS; upstream has no LICENSE
  file but author has stated FOSS intent).

- pyproject.toml — renamed project to `memoria`, removed unused
  python-dotenv dependency, added optional `test` dep group.

- scripts/fs_utils.py — NEW module containing the primitives that
  the other patches rely on:
    * atomic_write_text(path, content): tmp + fsync + os.replace;
      interrupted writes leave the target unchanged.
    * locked_append_text(path, content): fcntl.flock (POSIX) /
      msvcrt.locking (Windows) exclusive lock around the write so
      concurrent callers never interleave.
    * extract_wikilinks / parse_wikilink: strip [[target|display]]
      aliases correctly (fixes upstream issues #7 and #8).
    * safe_article_path(link, base): resolves a wikilink slug inside
      a base dir or returns None (path traversal guard).
    * load_json_with_recovery(path, default): on corruption, moves
      the bad file aside with a timestamped .bak-YYYYMMDDTHHMMSSZ
      suffix, logs a warning, returns the default. Replaces the
      silent `{}` return that would otherwise cause full-recompile.

- scripts/utils.py — save_state/load_state now use atomic writes and
  corruption recovery; wiki_article_exists + count_inbound_links now
  alias-aware via fs_utils helpers.

- scripts/config.py — TIMEZONE is now wired via zoneinfo.ZoneInfo
  and used by now_iso/today_iso (previously defined but ignored).
  Overridable via MEMORIA_TZ env var. Unknown zones log a warning
  and fall back to system local time rather than crashing.

- scripts/flush.py —
    * save_flush_state / load_flush_state use atomic + recovery.
    * append_to_daily_log uses locked_append_text; concurrent flush
      + pre-compact calls can no longer interleave log entries.
    * run_flush retries SDK failures up to MAX_SDK_ATTEMPTS=3 with
      exponential backoff (2s, 4s) before returning FLUSH_ERROR.
    * On FLUSH_ERROR, main() preserves the context file and does NOT
      update dedup state — the next flush retries cleanly instead of
      the failure being silently swallowed.
    * Explicit model="haiku" for flush (short summarization task).
    * maybe_trigger_compilation replaced: 6 PM wall-clock gate is
      gone; trigger is now staleness-based (hash changed AND
      COMPILE_INTERVAL_MIN elapsed since last compile). Configurable
      via MEMORIA_COMPILE_INTERVAL_MIN. Uses _now_local() from
      config so the clock respects the configured timezone.
    * compile.log handle uses a `with open()` context manager so the
      fd is always cleaned up, even if Popen throws.

- hooks/session-end.py, hooks/pre-compact.py — subprocess.Popen now
  passes start_new_session=True on POSIX, detaching flush.py from
  the hook's process group so it survives post-hook SIGHUP. Fixes
  the intermittent-data-loss failure mode where flush subprocess
  was killed mid-LLM-call.

Tests (formal acceptance suite still to come in this phase): each
helper verified via unit exercise in scratch directories — atomic
roundtrip, corruption recovery with .bak creation, alias parsing,
path-traversal rejection.

Upstream issue mapping: #3/#5/#9 addressed by the next commit
(compile.py + query.py scaling fix). #7/#8 addressed here via
alias-aware helpers. License (#11) resolved via MIT LICENSE.

hooks/pre-compact.py

@@ -152,15 +152,19 @@ def main() -> None:
         session_id,
     ]
 
-    creation_flags = subprocess.CREATE_NO_WINDOW if sys.platform == "win32" else 0
+    # On POSIX, start_new_session=True detaches the flush subprocess from the
+    # hook's process group so it survives CC's post-hook cleanup signals.
+    popen_kwargs: dict = {
+        "stdout": subprocess.DEVNULL,
+        "stderr": subprocess.DEVNULL,
+    }
+    if sys.platform == "win32":
+        popen_kwargs["creationflags"] = subprocess.CREATE_NO_WINDOW
+    else:
+        popen_kwargs["start_new_session"] = True
 
     try:
-        subprocess.Popen(
-            cmd,
-            stdout=subprocess.DEVNULL,
-            stderr=subprocess.DEVNULL,
-            creationflags=creation_flags,
-        )
+        subprocess.Popen(cmd, **popen_kwargs)
         logging.info("Spawned flush.py for session %s (%d turns, %d chars)", session_id, turn_count, len(context))
     except Exception as e:
         logging.error("Failed to spawn flush.py: %s", e)