resampling typo silently becomes "near" in dft_stac_cube / dft_stac_composite / dft_stac_fetch

[NewGraphEnvironment]

Problem

resampling goes straight into gdalcubes::cube_view(). The mechanism is the same one that #92 hit for aggregation: gdalcubes 0.7.5 reads a value it does not know as a default and raises no error. For resampling that default is "near".

Measured by round-tripping values through cube_view(...)$resampling:

bilinear -> bilinear
bilinaer -> near
foo      -> near
Bilinear -> bilinear     # case-insensitive
cubic    -> cubic

So dft_stac_cube(aoi, resampling = "bilinaer") returns a nearest-neighbour cube and caches it under the misspelt key, with no warning. The three callers are stac_cube_assemble() (R/dft_stac_cube.R, used by the cube and the composite) and fetch_extent_to() (R/dft_stac_fetch.R).

Ask

Validate resampling the same way #92 validates aggregation:

• Build the allowed set by measuring the cube_view() round trip, not from ?cube_view.
• Match case-insensitively.
• Run the check before any network call.
• Pin the set with a behaviour test.

Found by the /code-check round-3 review on #92.

Landed (#98, v0.21.0)

The full round trip on gdalcubes 0.7.5 found more than the five values above:

• Twelve come back unchanged and form the allowed set: near bilinear cubic cubicspline lanczos average mode max min med q1 q3.
• Two are honoured under another name: mean -> average and median -> med. These are refused, and the error names the spelling to use, so each method has one spelling. Refusing them breaks calls that used to give correct output, hence a minor release.
• Everything else becomes near, including GDAL's sum, rms and gauss, plus nearest.

The check runs at all three entry points and again at both cube_view() call sites. fetch_extent_to() also gained the #92 aggregation_check() it lacked.