Bundle the site's typefaces in the Android app

[octopranav]

What changes

• The app has been set in the device's serif, sans and monospace faces as stand-ins. It now carries the site's three typefaces, each in its role:

  • Bitter for display
  • IBM Plex Sans for body text
  • IBM Plex Mono for codes and labels

• designsystem/src/main/res/font/ holds five files from the google/fonts repository, byte for byte:

  File	Upstream
  bitter.ttf	ofl/bitter/Bitter[wght].ttf (variable)
  ibm_plex_sans.ttf	ofl/ibmplexsans/IBMPlexSans[wdth,wght].ttf (variable)
  ibm_plex_mono_regular.ttf	ofl/ibmplexmono/IBMPlexMono-Regular.ttf
  ibm_plex_mono_medium.ttf	ofl/ibmplexmono/IBMPlexMono-Medium.ttf
  ibm_plex_mono_semibold.ttf	ofl/ibmplexmono/IBMPlexMono-SemiBold.ttf

• Both OFL licence texts ship in the app's assets, as the licence requires.

• Theme.kt points each role at its family. Every weight the scale uses is set on the variable fonts' weight axis.

• audit/fonts.py pins each font to the git hash of its upstream file. It also requires each licence to be present and still name its reserved font name. It comes with tests and a CI step.

Why unmodified

Both licences reserve the name: "Bitter Pro" for Bitter, "Plex" for IBM Plex. A subset or a merged copy of the site's WOFF2 files would be a modified version still carrying the reserved name. So the originals are bundled, and the audit keeps them original: a font saved again by a tool renders the same and breaks the licence silently.

Checks

• Every downloaded file matched the git hash the GitHub contents API reports for it upstream. The staged objects carry the same hashes.
• python audit/fonts.py passes, and the audit tests pass: 51 in all, 8 new. The new tests cover a changed byte, a missing font, an unpinned font, a missing licence, and a licence without its reserved name.
• Emulator: Bitter semibold in the emergency card's title, Plex Sans in body text, Plex Mono in codes with its dotted zero.
• The explicit axis setting matters. Built without it, Bitter drew "Where I am" in its thinnest master, with about a sixth of the ink of the semibold.
• The APK grows by about 0.6 MB compressed (1.3 MB installed).