feat(brand): render the dashboard and documentation favicons from the app icon vector

[lidge-jun]

Summary

• docs-site/public/favicon.png was the dark variant of the mark: white on transparency, 192px, 36225 of 36864 pixels carrying some alpha but every one of them RGB (255,255,255), exactly one fully opaque pixel, corner (255,255,255,3). Composited on white it is a white square, and a browser tab strip is light by default, so the documentation site effectively had no favicon in light mode. favicon.ico beside it carried the same artwork at 16, 32 and 48, also with no fully opaque pixel.

• The dashboard favicon looked right at 128 but was a bitmap no source could regenerate, and it was the shaded artwork whose engraved prompt all but disappears at 16 and 32. Rendering the vector at 128 differs from it in 68% of pixels — a visible simplification, the same trade the app icon made in feat(desktop): draw the app icon and menu bar mark from the brand artwork #5355.
• Both are now rendered from desktop/src-tauri/icons/icon.svg at the names, sizes and formats the two sites already reference, so neither page nor config changes.
• The renderer, the RGBA re-encode and the ICO packer move into scripts/lib/icon-render.ts so both generators share them. A second copy of the PNG re-encode would be a second place for the alpha bug in fix(desktop): keep the alpha channel every generated icon needs #5356 to come back.
• The test decodes pixels because an opaque corner alone is not enough: a plain white square has an opaque corner and is still invisible. It requires an opaque light corner and at least 10% of the image to be opaque pixels whose luminance differs from that corner by more than 64.
• Out of scope, recorded rather than fixed: Starlight's logo-light.png and logo-dark.png stay as they are, since they are the artwork the vector was traced from rather than derived assets. og.png also stays, and carries its own pre-existing mismatch — the config declares 1200x630 and the file is 1536x1024.

Rationale and measurements: devlog/_plan/260921_brand_icon_and_menu_bar_mark/010_favicons.md.

Verification

• bun run favicons then bun run favicons:check — 3 favicons regenerated, 3 matching.
• cd desktop && bun run icons:check — 18 matching, so the extraction did not change the app icon bytes.
• bun test tests/ci-workflows/brand-favicons.test.ts tests/ci-workflows/build-desktop-icon-set.test.ts tests/test-layout.test.ts tests/test-layout-tooling.test.ts — 30 pass, 0 fail.
• Non-vacuous, both ways of being invisible applied one at a time: the white-on-transparent artwork this replaces gives 3 pass / 1 fail, and a solid #fcfcfc square gives 3 pass / 1 fail. The generated favicons give 4 pass / 0 fail.
• bun run privacy:scan and bun run structure:check pass.
• Full suite and typecheck were NOT run here; hosted CI is the gate for those.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-20T17:10:02.586564Z	3fa1729	PR opened

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Reviewing files that changed from the base of the PR and between 480c1c7 and 3fa1729.

⛔ Files ignored due to path filters (4)

• assets/pr-screenshots/favicon-light-tab.png is excluded by !**/*.png
• docs-site/public/favicon.ico is excluded by !**/*.ico
• docs-site/public/favicon.png is excluded by !**/*.png
• gui/public/favicon.png is excluded by !**/*.png

📒 Files selected for processing (8)

• desktop/scripts/generate-icons.ts
• devlog/_plan/260921_brand_icon_and_menu_bar_mark/010_favicons.md
• package.json
• scripts/brand-favicons.ts
• scripts/lib/icon-render.ts
• scripts/test-layout/layout.json
• tests/ci-workflows/brand-favicons.test.ts
• tests/fixtures/test-layout-expected.json

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