Header channel-logo overflows the document by 7px at 375px

[prekabreki]

Context

Measured during #51's responsive check on 2026-08-01: at a 375px viewport the document
overflows horizontally by 7px (document.documentElement.scrollWidth - clientWidth === 7),
sourced from #channel-logo in the header. The Advanced panel itself measured 0, so this is
pre-existing and unrelated to that work — it just had never been measured before.

Horizontal scroll at phone width is a real defect, and the header is the first thing on the
page.

Acceptance criteria

• At 375px, document.documentElement.scrollWidth - document.documentElement.clientWidth === 0.
• The channel logo is still visible when a channel is resolved, at its current size.
• Its space is still reserved before load — the logo fades in on load (Animate the four unbridged reveals and the shutdown overlay's exit #48) and must not
  reintroduce layout shift.
• No regression at 768px and 1440px (both currently measure 0).

Files / where this lives

• fetchforge/index.html:77 — .channel-logo CSS
• fetchforge/index.html:1225 — the <img id="channel-logo"> element
• The surrounding header/hero row is the likely real culprit (a fixed width plus padding
  exceeding the viewport), so check the container, not only the image.

How to verify

• Serve on a spare port (not 8765) and, at a 375px viewport with a channel resolved, assert
  the document scrollWidth delta is 0. tests/frontend/ exists but is jsdom, which does no
  layout — this needs a real browser.
• npx impeccable detect fetchforge/index.html still exits 0.

Constraints

• Preserve: the logo's fade-in on load and its reserved space (both from Animate the four unbridged reveals and the shutdown overlay's exit #48).
• Match: DESIGN.md's layout rules — 900px max content width, no new breakpoints unless needed.

Out of scope

• Any other responsive work; this is the one measured overflow.

Notes

• Executor tier: cheap.