Give the CI build its own Windows icon, and pin Flutter once per workflow

[JoshuaLampert]

Two small things, both from the Linux/Windows packaging work.

The Windows CI build had no icon of its own

It was distinguishable from the released app only by its window title. tool/build_ci_icon.py — which already composes the mark with an amber CI chip for Android — now also writes windows/runner/resources/app_icon_ci.ico, and Runner.rc picks it under PAPPUS_SIDE_BY_SIDE.

• Cropped to what is actually drawn: the adaptive icon's canvas is mostly the margin a launcher mask needs, and a desktop icon has no mask, so uncropped the mark would sit small in its own box on the taskbar.
• Every size Windows asks for (16 … 256) in the one file, since it scales whatever it does not find, and a blurred 256 is what a 16px taskbar icon then looks like.
• The Android files it writes come out byte-identical, so re-running the script changes only the new file.

The Flutter version was pinned seven times

Four times in ci.yml, three in release.yml. A bump that reached some of them would leave jobs testing and building against different SDKs. It is now one env: per workflow, and the reasoning about the range (3.47.x) versus the exact pin (3.47.2, the line an F-Droid recipe reads) moved up there with it.

Verified

• The icon renders as intended at 128px, and the file carries all seven sizes.
• Both workflows still parse.
• Not verified: the icon on a real taskbar, and the workflows themselves — this PR's run is that test for ci.yml, while release.yml needs a dry run.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!