[sx4im]

What

A new Linux-only preflight check runs fc-list before the browser launches. Zero fonts fails the render with the fix in the hint, and doctor shows the font count.

Why

On Linux, when fontconfig lists zero fonts, hyperframes render exits 0 and every frame comes out with no text at all, even though HyperFrames embeds a web font. doctor passed too, so there was no hint anything was wrong.

Related work

Fixes #7406

How

checkSystemFonts() in packages/cli/src/browser/preflight.ts counts non-empty fc-list lines and joins runEnvironmentChecks() when the browser is included, so render stops on the failed outcome and doctor lists it. A missing or failing fc-list only warns, since the binary on PATH may not be the fontconfig Chromium loads. Off Linux the check is a no-op.

Test plan

How was this tested?

• Unit tests added/updated
• Manual testing performed
• Documentation updated (if applicable)
• Comments follow CONTRIBUTING.md "Comments": they say why, not what, and a bug fix says what the code must do and how to reproduce the bug

New tests in packages/cli/src/browser/preflight.test.ts: 0 lines fails, N lines passes, missing or failing fc-list warns, no-op off Linux. 39 preflight tests and 34 doctor tests pass, CLI typecheck is clean, oxlint and oxfmt are clean. Ran the built CLI here: doctor reports System fonts: fontconfig fonts: 1877, matching fc-list on this machine.

Note: check and snapshot do not run the shared preflight, so they are not covered by this change.

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