Shorten firmware picker selection links and keep original download names

Replace the download-file shortcut approach with compact self-contained picker URLs under /p/. Preserve long-link compatibility, selected install formats, and full published firmware filenames. Cover selection round trips and the redirect in the picker tests.

.github/workflows/github-pages.yml

@@ -23,12 +23,6 @@ jobs:
         with:
           python-version: '3.13'
 
-      - name: Preserve published firmware short-link identities
-        run: |
-          python scripts/check_published_firmware_shortlinks.py \
-            --manifest docs/_data/firmware_shortlinks.json \
-            --previous "$RUNNER_TEMP/previous-firmware-shortlinks.json"
-
       - name: Build
         env:
           GH_TOKEN: ${{ github.token }}
@@ -38,8 +32,6 @@ jobs:
           MKDOCS_EDIT_URI: edit/${{ github.ref_name }}/docs/
         run: |
           pip install mkdocs-material
-          python -B test/test_firmware_shortlinks.py -v
-          python -B test/test_docs_firmware_shortlinks.py -v
           node test/test_firmware_picker.js
           node test/test_partition_catalog_viewer.js
           python scripts/sync_bootloader_manifest.py