Embed installed SVG fonts before capture

[jackspirou]

Set FontFamily "Menlo" now embeds the installed face for SVG output when Fontconfig is available. The selected bytes load before terminal sizing and capture. Optional FontTools subsets displayed terminal, cursor, and title glyphs, with full-face fallback on failure.

This completes the automatic setup and file-size benefits from #8 and retains its original commits. Explicit flag and environment paths take priority and preserve exact bytes, including video-only capture. Separate title fonts and collection face indices remain distinct. Generic families and fallback stacks retain their current behavior.

The repair escapes font names at the JavaScript, CSS, and XML boundaries. It preserves raster title families, prepares output fonts before successful browser teardown, and tests final even viewport dimensions to prevent an extra column.

Validation:

• Full native race suite passes 336 cases and 113 top-level tests, with no failed or skipped tests. Earlier checks had two transient startup failures. The report preserves those logs and the passing unchanged-source rerun.
• Real tape evaluation produces a 5,000-byte font payload versus 231,000 bytes full and retains required Unicode glyphs. Native capture and SVG advances match in automatic, flag, and environment modes.
• A real installed-font CLI capture discovers Menlo and a separate Helvetica Neue title face. The saved SVG has two WOFF2 subsets with preserved glyphs and advances.
• Missing or failed tools, invalid metadata and files, browser rejection, and cancellation have regression coverage. Tests also cover collections, explicit priority, video-only font files, and injection.
• Vet, lint, build, tidy, formatting, diff checks, and 106 tape checks pass. Native rendering evidence covers macOS and Chrome. Linux and Windows native rendering remains UNVERIFIED.

The contributor fork rejected the authenticated LFS lock check during a dry-run push. This replacement uses an owned branch and preserves the contributor’s published history.

Pre-PR autoreview passes with no P0 findings. The exact-content secret scan is clean.

Resolves #8.