Typeahead doesn't match colon-namespaced plugin commands by namespace prefix

Description

When typing a slash command prefix that matches a plugin namespace (e.g., /agentem), the typeahead autocomplete does not show any of the colon-namespaced commands from that plugin (e.g., /agentem:doctor, /agentem:init, /agentem:sprint-plan). The commands are registered and execute correctly when typed in full — they are just completely absent from the typeahead index.

Steps to Reproduce

1. Install a plugin that registers colon-namespaced slash commands (e.g., agentem:doctor, agentem:init, agentem:sprint-plan, agentem:context-loader)
2. Open Claude Code and type /agentem in the input
3. Observe the typeahead dropdown

Expected Behavior

The typeahead should show all /agentem:* commands when typing /agentem.

Actual Behavior

• Typing /agentem only shows /agents (a built-in command). None of the /agentem:* plugin commands appear.
• Typing /age shows /agents, several /Notion:* commands (from an MCP-based plugin), and other built-in commands — but still zero /agentem:* commands, despite "age" being a direct prefix match on "agentem".
• Typing the part after the colon (e.g., /doctor) does find the plugin command, showing it alongside matching built-in commands.
• Typing the full command (e.g., /agentem:doctor) and submitting it works correctly — the command executes fine.

Key Observation

The /Notion:* commands (registered via MCP plugin) appear correctly in typeahead results. The /agentem:* commands (registered via skill/slash-command plugin) do not appear at all — they seem to not be indexed by the typeahead fuzzy matcher. This suggests the typeahead indexes commands differently depending on their registration method, and non-MCP plugin commands may be excluded from the index entirely.

Searching by the part after the colon (e.g., /doctor finds agentem:doctor) confirms the commands are registered — they're just not discoverable via prefix search on the namespace.

Environment

• Claude Code v2.1.50
• macOS (Darwin 24.6.0)
• Plugin commands confirmed registered and functional — only the typeahead matching is affected

Related Issues

This appears to be a separate symptom of the same underlying autocomplete system not being namespace-aware. The issues below cover commands not appearing or losing prefixes; this issue covers the fuzzy match algorithm not treating the colon as a meaningful separator.

• #17509
• #22063
• #6946