bug(remote): feed symbols render as Apple color emoji on the phone

[Juliusolsson05]

Summary

The phone companion shows Apple color emoji where the desktop shows monochrome symbols. The worst case is the ⏺ tool bullet on every Claude row. This has come back after several attempts to fix it.

Root cause

• Where the characters come from. The phone mounts the desktop's own feed rows (refactor(remote): put the phone on the desktop's rendering seams #1186), and those rows use symbol characters that have the Unicode Emoji property:
  • ⏺ U+23FA: 29 uses, the Claude tool bullet
  • ⏸ U+23F8
  • ☑ U+2611 and ☐
  • 🖼 U+1F5BC
  • ↗ U+2197
• Why the fonts don't catch them. The app font stack is 'JetBrains Mono', ui-monospace, Menlo, Monaco, monospace, and JetBrains Mono has no glyph for ⏺ ⏸ ☑ 🖼. I verified this against the font's cmap.
• Why only the phone is affected. On macOS, Chromium falls back to a monochrome system symbol font. iOS Safari has no such font, so it falls back to Apple Color Emoji.
• Why earlier fixes didn't stick. They replaced emojis in the phone's own chrome with bundled SVG icons (5ad922cf). The shared rows were never covered, so the symbols reappeared wherever a row drew one.

Fix

Put monochrome symbol fonts that verifiably contain these glyphs into every app font stack, ahead of the system fallbacks:

• Noto Sans Symbols 2 covers ⏺ ⏸ ☑ ☐ 🖼 ✓ ✗ ◐ ◌ ▸ ▾ ❯ ● ✕ ⌘.
• Noto Sans Symbols covers ↗.

Both are served by the Google Fonts import the app already uses, and they only download the subsets for characters that are actually drawn.

Acceptance criteria

• Every font option's stack names the symbol fallbacks before the system generics. A test pins this.
• Both the desktop and the phone use the same stack.
• Emoji that agents write in their own text (✅ etc.) are content and still render as emoji on both clients. That is unchanged and deliberate.

[Juliusolsson05]

Fix approach changed in review (see #1196). The app-wide Noto font stack was reverted: it turned agent-written emoji monochrome, iOS's ui-monospace expansion could still reach Apple Color Emoji first, and it depended on the Google Fonts CDN. The shipped fix is phone-only. The phone gets a bundled, unicode-range-scoped symbol face (Noto subsets for ⏸ ⏺ ☐ ☑ 🖼 ↗ ↩) placed first in its font stack, and a test checks coverage of every emoji-property symbol in the phone's import graph.