/fast slash command has no effect on Desktop app (Windows, Team plan)

Description

The /fast slash command does nothing on the Claude Code Desktop app (Windows). No toggle, no lightning icon, no error message - it is silently ignored. The fastMode: true setting in ~/.claude/settings.json is also not applied on startup.

This is distinct from #24351 (which was CLI-specific and is now closed). The Desktop app appears to not support /fast at all.

Steps to reproduce

1. Set fastMode: true in ~/.claude/settings.json
2. Enable fast mode and extra usage in Team org admin settings
3. Open Claude Code Desktop app (Windows)
4. Type /fast and submit
5. Observe: nothing happens, no lightning icon, no feedback

Additional testing done

• Removed all custom skills (~/.claude/skills/) to rule out autocomplete conflicts - same result
• Added keybinding {keys: ctrl+shift+f, command: chat:fastMode} - no effect
• Org admin has fast mode enabled + extra usage enabled + available balance

Expected behavior

/fast should toggle fast mode and show the lightning icon, same as in CLI.

Actual behavior

/fast is silently ignored. No toggle, no icon, no error message.

Environment

• Claude Code Desktop app (Windows 11 Home 10.0.26200)
• Claude Code CLI v2.1.92 (installed via npm)
• Team plan (3 seats)
• Fast mode enabled by org admin
• Extra usage enabled with available balance