docs(models): rename Qwen3.8-Max to Qwen3.8-2.4T-A95B (#3549)

Align the model coverage page, Fern nav entry, HellaSwag EP32/PP8 recipe,
and README links with the published checkpoint id Qwen/Qwen3.8-2.4T-A95B.
Adds a redirect so the previous nightly model-coverage URL keeps working.

Signed-off-by: Huiying Li <willwin.lee@gmail.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>