fix(ci): stop setup-android installing a package Google has removed

**Unrelated to this PR's feature work**, and fixed here because it blocks
verifying it (org lead, 2026-09-17). PR #46 passed on this workflow yesterday;
every Android PR fails now.

`android-actions/setup-android@v3` is a floating tag and the action's `packages`
input defaults to `tools` — an obsolete package Google has since removed from the
SDK repository. So the step runs `sdkmanager tools`, gets `Warning: Failed to
find package 'tools'`, exits 1, and CI fails in **Set up Android SDK**, before a
line of this repo is compiled.

`packages: ''` turns that install off. It was always redundant here: the very
next step installs exactly what the build targets — `platform-tools`,
`platforms;android-35`, `build-tools;35.0.0` — precisely so the build never
depends on what some action decided to fetch.

Not addressed here, and worth its own decision: `@v3` is a floating major tag, so
the next upstream change can break CI the same way without warning.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016wDDVXWMDz82WqE1i969r4

.gitea/workflows/pr-checks.yml

@@ -45,8 +45,15 @@ jobs:
 
       - uses: actions/checkout@v4
 
+      # `packages: ''` is load-bearing, not tidying. The action's own default is
+      # `tools` -- a package Google has REMOVED from the SDK repository -- so the
+      # default makes `sdkmanager tools` exit 1 and the step fails before a line
+      # of this repo is compiled. It is redundant here regardless: the next step
+      # installs exactly what the build targets.
       - name: Set up Android SDK
         uses: android-actions/setup-android@v3
+        with:
+          packages: ''
 
       # Install exactly what the build targets so it never depends on AGP's
       # build-time auto-download. `yes |` accepts any license prompts; `set