Audit GeoTIFF example notebooks for unsupported-as-stable wording (#2345 PR 4) #2382

Part of epic #2345.

Goal

Audit the GeoTIFF-touching example notebooks so they do not imply unsupported, experimental, or advanced behavior is part of the stable release contract.

Scope

Walk these notebooks under examples/user_guide/:

• 25_GLCM_Texture.ipynb
• 29_Preview.ipynb
• 39_GeoTIFF_IO.ipynb
• 40_JPEG2000_Compression.ipynb
• 46_GeoTIFF_Performance.ipynb
• 47_Streaming_GeoTIFF_Write.ipynb
• 52_COG_Overview_Generation.ipynb

For each notebook:

• Add a tier callout near the top when the notebook is exercising an advanced or experimental path (notably JPEG2000, which is experimental).
• Trim or rewrite cell text that implies a path is stable when SUPPORTED_FEATURES says otherwise.
• Add a short "see also" pointer at the top to docs/source/reference/geotiff.rst so a reader can find the release contract.

Out of scope

• Changing the data the notebooks load.
• Restructuring the notebook narratives beyond the callout / pointer additions.
• Adding new notebooks.

Acceptance

• Every notebook in scope has either a tier callout (when on an advanced / experimental path) or an explicit statement that it exercises the stable contract.
• No notebook claims full GDAL / VRT / GPU / codec parity.
• The notebooks still execute end to end under the existing CI.