Adds patch 0023 (Path B build fixes per fathyb#27). Carbonyl now builds
cleanly on M135. headless_shell links and binary runs.

The b64 text-capture mode (--carbonyl-b64-text) is disabled in this
build because its blink/renderer/core reach triggers an Oilpan/cppgc
cascade in M135. Bitmap rendering (the default) is unaffected. Path A
(fathyb#28) restores the feature via a real blink TU and is the structural
fix that gates all rebases past M135.

Closes fathyb#27.
Refs: fathyb#20, fathyb#28, fathyb#29, fathyb#30.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- changelog.md: M135 marked as SHIPPED with patch 0022/0023 details,
  full b64 text capture removal note, runtime tarball link, CI section
- readme.md: bump from "M120, M135 in progress" to "M135 shipped",
  add carbonyl-agent reference, document b64 text limitation
- MAINTENANCE.md: 23-patch breakdown, Path B/Path A explanation,
  M135 GN args quirks (left at platform defaults)
- src/browser/host_display_client.{cc,h}: drop dead X11 path
  (ozone_platform_x11 = false in this build) — found during M135 build
  triage; removes a buildflag include cascade

Refs: fathyb#20 fathyb#27 fathyb#28