[FEATURE] Allow configuring slash command priority/ordering

Problem

When installing plugins or custom skills, their slash commands can collide with built-in commands in the / autocomplete menu. There is no way to configure which command takes priority when typing a prefix.

Example

A user installs a plugin with a skill named query-databricks. Now when they type /q, the autocomplete suggests query-databricks instead of the built-in /quit command. The user has years of muscle memory typing /q to exit, and now it resolves to the wrong command.

The only workarounds today are:

• Rename the plugin/skill to avoid the prefix collision (e.g., databricks-query)
• Type the full command name every time
• Give up and use Ctrl+C / Ctrl+D instead

None of these are great — the user shouldn't have to rename third-party plugins, and typing full command names defeats the purpose of autocomplete.

Proposed Solution

Allow users to configure slash command priority or ordering, for example:

1. Priority field in skill frontmatter — e.g., priority: 10 so higher-priority commands sort first in autocomplete
2. User-level config in settings.json — e.g., a slashCommandPriority map that lets users pin specific commands to the top or define a preferred resolution order
3. Aliases — Allow users to define custom short aliases for commands (e.g., /q → /quit)
4. Built-in commands always win — A simpler option: built-in commands (/quit, /help, /clear, etc.) should always take precedence over plugin commands in autocomplete when there's a prefix collision

Any of these would solve the problem. Option 4 is the simplest, but options 1-3 give users more control.

Why This Matters

As the plugin/skill ecosystem grows, prefix collisions will become increasingly common. Users develop muscle memory for short prefixes, and a single plugin install silently breaking that muscle memory is a poor experience.