ci: stop keeping godot and hwci artifacts for 90 days

[bwhitman]

Per-platform godot bins are an intermediate for the package job (retention 1 day); the addon zip and hwci logs keep 7. At the repo default of 90 days these were ~1.8 GB of the shorepine account's Actions storage quota.

🤖 Generated with Claude Code

[bwhitman]

Just CI stuff, ima merge

[github-actions]

🎛️ AMY HW CI (AMYboard bench)

Flashed this PR's AMY (LoadTestChord: 6-voice Juno patch=1, one held note every 2 s) onto the physical AMYboard and measured the smoothed render load as the chord grows — back-to-back with the same sketch built at the PR's merge base, so Δ is this PR's own cost.

✅ PASS — the bench ran the test to completion.

notes held	main @ e4881fa	this PR	Δ
1	976	976	+0
2	1133	1133	+0
3	1702	1702	+0
4	1872	1873	+1
5	2458	2458	+0
6	2595	2595	+0

Full chord settled render μs: 2596 (was 2596, Δ +0.0%) (peak 2602, 39 samples)

⬇️ Artifacts: serial log · load trace · report

_{Self-hosted bench (amyboardci). FAIL means only that the test could not run — the load values are informational, with no threshold and no audio compare. See tools/arduino_loadsweep/.}