fix(tests): isolate LocalFileStorage session dir from the real home dir (#16)

test_mcp_server.py constructs LocalFileStorage() with no storage_dir,
which defaulted to the developer's real ~/.attune-help/sessions/ — so
running the suite leaked session files there (it had accumulated 800+).
attune-help's conftest had no isolation for it and the default path was
hardcoded inline (not overridable).

- storage.py: make the default dir overridable via ATTUNE_HELP_SESSIONS_DIR
  (new _default_storage_dir helper).
- conftest.py: autouse fixture points it at a tmp dir for the whole suite.

Verified: real sessions count is unchanged across a full 338-test run
(previously grew every run).

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: silversurfer562

src/attune_help/storage.py

@@ -9,6 +9,7 @@
 
 import json
 import logging
+import os
 import time
 from pathlib import Path
 from typing import Any, Protocol
@@ -17,6 +18,16 @@
 
 _SESSION_TTL_SECONDS = 4 * 3600  # 4 hours
 
+# Default on-disk location for session files. Overridable via the
+# ``ATTUNE_HELP_SESSIONS_DIR`` env var so tests/CI never touch the
+# developer's real ``~/.attune-help/sessions/``.
+_DEFAULT_SESSIONS_DIR = "~/.attune-help/sessions"
+
+
+def _default_storage_dir() -> Path:
+    """Resolve the default session directory (env-overridable)."""
+    return Path(os.environ.get("ATTUNE_HELP_SESSIONS_DIR", _DEFAULT_SESSIONS_DIR)).expanduser()
+
 
 class SessionStorage(Protocol):
     """Protocol for session state backends.
@@ -161,7 +172,8 @@ class LocalFileStorage:
 
     Args:
         storage_dir: Directory for session files.
-            Defaults to ~/.attune-help/sessions/.
+            Defaults to ~/.attune-help/sessions/ (overridable via the
+            ``ATTUNE_HELP_SESSIONS_DIR`` env var).
         ttl_seconds: Session time-to-live in seconds.
             Defaults to 4 hours.
     """
@@ -172,7 +184,7 @@ def __init__(
         ttl_seconds: int = _SESSION_TTL_SECONDS,
     ) -> None:
         if storage_dir is None:
-            self._dir = Path("~/.attune-help/sessions").expanduser()
+            self._dir = _default_storage_dir()
         else:
             self._dir = Path(storage_dir)
         self._ttl = ttl_seconds

tests/conftest.py

@@ -11,6 +11,17 @@
 PYPROJECT = REPO_ROOT / "pyproject.toml"
 
 
+@pytest.fixture(autouse=True)
+def _isolated_sessions_dir(tmp_path, monkeypatch):
+    """Redirect LocalFileStorage's default session dir to a tmp path.
+
+    Without this, tests that construct ``LocalFileStorage()`` with no
+    ``storage_dir`` (e.g. test_mcp_server.py) read from / write to the
+    developer's real ``~/.attune-help/sessions/``.
+    """
+    monkeypatch.setenv("ATTUNE_HELP_SESSIONS_DIR", str(tmp_path / "sessions"))
+
+
 @pytest.fixture
 def plugin_root() -> Path:
     """Absolute path to the plugin directory."""