muxg: missing ⏵⏵ glyphs and incorrectly rendered Claude icon

open   by a73x

Labels: backlog, gui

The native GUI (muxg) has two reported glyph rendering problems:

- `⏵⏵` does not render.
- The Claude icon renders incorrectly.

Font coverage or fallback is suspected, but the cause is not confirmed. The exact Claude icon glyph/sequence, affected OS, and configured font still need to be captured during reproduction.

Investigate font selection, fallback, glyph rasterization, and cell placement in the GUI. Reproduce with literal `⏵⏵` output and the actual Claude icon, comparing the same session in a terminal that displays them correctly.

Acceptance criteria:
- Both `⏵` characters in `⏵⏵` are visible and correctly placed.
- The Claude icon renders correctly without missing glyphs, clipping, or broken alignment.
- Verify the fix in the real GUI and add appropriate regression coverage for the confirmed cause.