nldi: raise ValueError (not TypeError) for invalid navigation mode

[thodson-usgs]

Summary

_validate_navigation_mode raises TypeError for an invalid string value (e.g., "XX"). The sister helper _validate_data_source in the same file already raises ValueError for the same kind of bad-input case. TypeError is reserved for cases where an arguments type is wrong; an unrecognized navigation-mode string is a value error, so callers writing except ValueError: would not catch it today.

# dataretrieval/nldi.py:486-489
def _validate_navigation_mode(navigation_mode: str):
    navigation_mode = navigation_mode.upper()
    if navigation_mode not in ("UM", "DM", "UT", "DD"):
        raise ValueError(f"Invalid navigation mode '{navigation_mode}'")  # was TypeError

One-line change; no regression test (the assertion would just re-state the diff).

Related PRs

This is a strict subset of #252 (nldi-cleanup), which also changes TypeError -> ValueError here as part of a larger refactor (extracts _VALID_NAVIGATION_MODES, normalizes input and returns it, adds a None guard). If #252 lands first, this PR can be closed.

#246 (nldi-data-source-validation) also touches nldi.py but a different function (_validate_data_source); no conflict.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Aligns NLDI input validation semantics with Python conventions by raising ValueError (not TypeError) when a caller provides an unrecognized navigation-mode value, matching existing validation behavior in the same module.

Changes:

• Change _validate_navigation_mode to raise ValueError for invalid navigation mode strings.

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