#75 Responsive fixes: nav reachable at 390px, files table, clone summary wrapping

At 390px the site is usable-ish but broken in three specific places.

1. Nav is unreachable

.site-nav is display:flex;flex-wrap:wrap but .nav-scroll-row holds everything on one line, and body{overflow-x:clip} clips the overflow. At 390px only code · commits · issues (14) is visible — pulls, ci, releases, wiki, agents cannot be reached. No scroll affordance, no strip, no menu.

2. Files table is cramped, not scrollable

.file-scroll is deliberately exempt from the mobile card layout (m6/cards2, f0rge #46) and is supposed to scroll horizontally, but at 390px "Last commit" wraps to 3–4 lines per row while "Age" is clipped at the right edge. Row heights blow up, the table reads as broken rather than scrollable.

3. Clone summary wraps mid-token

Clone & download · master @ 6f379f8 · CI [pass] wraps so pass lands alone on line 2, and the summary line uses --muted (below AA).

Also

• Issue/PR meta blocks become six full-width lines on mobile (see the meta issue #72 — collapse to chips + <details>).
• Touch targets: nav links are min-height:40px (good); table row links are text-only; .btn-new is ~40px tall (good).
• No horizontal scroll indicator anywhere.

Scope

• Nav: one-row horizontally scrollable strip with edge fade (overflow-x:auto; scrollbar-width:none) or wrap into two rows; ensure every tab is reachable at 320/390/768. Keep aria-current.
• Files table: at <768px either drop the "Last commit" column (keep name + age, both real links), or let .file-scroll genuinely scroll with width:max-content and a scroll hint. Do not wrap commit subjects into 4 lines.
• Clone block: summary becomes a two-line block on mobile (title, then branch @ sha · CI badge), no mid-token wrap (white-space per segment / flex-wrap with gap).
• Test at 320, 360, 390, 768 (existing tests/responsive.rs can assert the rules, e.g. nav overflow-x and .file-scroll width behaviour).

Acceptance

• all 8 nav destinations reachable at 390px
• file table does not wrap commit subjects to >2 lines and does not clip the age column
• clone summary badge never splits from its label
• no page-level horizontal scroll at 390px