Storage default `D:/Gently3` is non-portable — creates a stray relative `D:` dir off-Windows

[subindevs]

Problem

StorageSettings.base_path defaults to a Windows drive path:

# gently/settings.py:73
base_path: Path = field(default_factory=lambda: _env("STORAGE_PATH", Path("D:/Gently3")))

On Windows (the microscope PCs) this is correct — D: is the dedicated data drive. But off-Windows (Linux dev boxes, macOS, CI), Path("D:/Gently3") is not an absolute path. It resolves relative to the cwd, so a default-config run silently creates a junk directory literally named D: and writes session data into it.

PR #51 added D:/ to .gitignore, which hides the symptom but doesn't stop the app from writing to a nonsense location.

Actual fix

Make the default platform-aware so Windows is untouched and everywhere else gets a real absolute path:

def _default_storage_path() -> Path:
    if os.name == "nt":
        return Path("D:/Gently3")
    xdg = os.environ.get("XDG_DATA_HOME")
    base = Path(xdg) if xdg else Path.home() / ".local" / "share"
    return base / "Gently3"

# ...
base_path: Path = field(default_factory=lambda: _env("STORAGE_PATH", _default_storage_path()))

• Windows production behavior is identical.
• GENTLY_STORAGE_PATH override is unchanged.
• The .gitignore D:/ entry becomes unnecessary (can be left as a stopgap).

Out of scope / follow-up

Other hardcoded D:/... defaults exist in legacy/script modules and could later route through settings.storage.base_path:

• gently/dataset/aggregator.py, embryo_dataset.py:164, schema.py:24 (DEFAULT_DB_PATH)
• benchmarks/perception/runner.py:493, diagnostics/segment_embryo_nuclei.py:57

Notes

Behavior change on non-Windows defaults → land as its own PR against development, not folded into release #51.

[pskeshu]

This is the way 😁