feat(paths): abstract runtime path logic for frozen distribution packages (#969)

* feat(core): abstract runtime path logic for frozen distribution packages

* Address review feedback: revert browser MCP check, persistent data dir default when frozen, and add path tests

src/runtime_paths.py

@@ -0,0 +1,30 @@
+"""Helpers for resolving runtime paths in source and frozen builds."""
+
+import os
+import sys
+
+
+def get_app_root() -> str:
+    """Return the app root directory.
+
+    In normal source runs, this is the repository root. In a frozen Windows
+    build, it is the bundle content root (PyInstaller's internal directory)
+    so bundled runtime folders like `static/`, `scripts/`, and `data/` stay
+    together with the executable payload.
+    """
+    if getattr(sys, "frozen", False):
+        return getattr(sys, "_MEIPASS", os.path.dirname(os.path.abspath(sys.executable)))
+    return os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+
+
+def get_default_data_dir() -> str:
+    """Return the default path to the data directory.
+
+    In normal runs, this is a 'data' subdirectory under the app root.
+    In frozen builds, it is a persistent user directory (~/.odysseus/data)
+    to prevent SQLite databases and other persistent files from being
+    written to the ephemeral, temporary extraction bundle directory.
+    """
+    if getattr(sys, "frozen", False):
+        return os.path.join(os.path.expanduser("~"), ".odysseus", "data")
+    return os.path.join(get_app_root(), "data")