Pin actionable failure modes for unsupported COG writer inputs (#2286 prod-ready wave B)

[brendancol]

Follow-up to #2286 (COG readiness).

Production-ready means predictable failure modes. Right now several unsupported to_geotiff(..., cog=True) input combinations may produce raw tracebacks from deep in the writer (or worse, succeed and produce a non-COG file). This issue pins each one to a typed exception with a remediation hint, and adds tests that lock the exception type and message in.

Required changes

New test file

xrspatial/geotiff/tests/test_cog_invalid_input_errors_2286.py.

For each row below, assert to_geotiff(arr, dst, cog=True, ...) raises a specific exception type with a message that names the violated constraint and tells the user what to do:

Input	Expected exception	Required message content
Experimental codec (e.g. compression='lerc') without allow_experimental_codecs=True	ValueError (or whatever the writer raises today — pin it)	Names the codec; tells user to set allow_experimental_codecs=True; mentions stability tier
Internal-only JPEG (e.g. compression='jpeg') without allow_internal_only_jpeg=True	(current writer behavior — pin it)	Names the codec; mentions allow_internal_only_jpeg opt-in
Rotated transform on input DataArray	(current writer behavior — pin it)	Names the rotated transform; mentions the rotated-CRS opt-in path
File-like / BytesIO destination with cog=True	(current writer behavior — pin it)	States that COG writes require a real path
CuPy / GPU-backed array with cog=True	(current writer behavior — pin it)	States GPU COG is not in the stable contract
Object-dtype DataArray	(current writer behavior — pin it)	Names the dtype; lists supported dtypes
Conflicting crs= and array CRS	already covered by #1929/#1987 — confirm message still actionable, don't duplicate

For each row:

1. If the writer already raises a sensible typed exception with an actionable message, the test just pins it (no production change).
2. If the writer raises a deep traceback (AttributeError, KeyError, struct format error, etc.) or silently produces a non-COG, add minimal validation at the public entry to convert it to a typed exception with a clear message.

Production code (minimal)

If any row needs a validation hook, add it in xrspatial/geotiff/_writer.py (or _attrs.py if it's a contract check) near the existing input-validation block. Reuse the existing exception types where possible; do not introduce a new exception class unless none of the existing ones fits.

Out of scope

• Promoting tiers (tracked separately).
• Documentation updates (tracked separately).
• Reader-side validation.
• Changing semantics of any path that currently succeeds.

Acceptance

• Each row above has at least one test that asserts the exception type and a substring of the message.
• All tests green.
• No silent path: every "out of scope" combo from the Promote COG support to ready/stable with compliance and parity gates #2286 list either raises with a clear message or is explicitly noted in the test file as already covered elsewhere.