fix: keep layout usable at high webview zoom and narrow widths

[gmcky]

At high webview zoom / narrow window widths the main layout broke: the header
title and controls overflowed, the language dropdown clipped at the viewport
edge, and long output tokens pushed past the pane.

What changed

• Header/toolbar: min-w-0 + shrink-0 guards; title truncates and hides
  under 800px; Translate button collapses to icon-only under 600px.
• LanguageSelector: dropdown now renders through createPortal to
  document.body with position: fixed; position is recomputed on
  resize / scroll / visualViewport, flips above the button when space below
  is tight, and clamps maxHeight to the viewport. Click-outside accounts
  for the portaled menu.
• Panes: fixed row layout with min-w-0; dropped the JS textarea auto-resize
  in favor of flex sizing so the counters stay visible.
• Output: break-words / overflow-wrap: anywhere so long tokens wrap
  instead of overflowing.
• Interface scale: capped max zoom at 170% (was 200%). Past ~170% on the
  minimum window size the header/toolbar overlapped and the language
  selectors slid off-screen; 200% was unreadable at that size anyway.

Testing done

Tested on Windows 11:

• Default window size
• Fullscreen at 1080p and 1440p
• High webview zoom + manually narrowed widths

@noxygalaxy could you sanity-check the visuals on Linux? I only have a
Windows machine to test on rn, so I'd like to confirm the tiling / resize
behavior and the portaled dropdown positioning hold up under a tiling WM
before this is merged. If anything looks off, just let me know and I'll
patch it up.

Verify

• Windows: header, dropdown, counters stay in viewport at high zoom
• Windows: Translate collapses to icon under 600px, title hides under 800px
• Dropdown flips up near the bottom edge
• Windows: max scale (170%) on minimum window keeps layout intact
• Linux / tiling WM: layout, resize, dropdown position confirmed (@noxygalaxy)

[noxygalaxy]

I will test that on linux asap