Feature request: bind keyboard shortcuts to custom slash commands in keybindings.json

Feature request

Allow ~/.claude/keybindings.json to bind a key (or chord) to invoking a custom slash command / skill, not only the built-in action list.

Problem

Today the action field in keybindings.json only accepts the fixed set of built-in actions. There is no way to express "pressing ctrl+s runs /sage" (a custom command defined in .claude/commands/ or a plugin skill). Power users who build custom agents/commands they invoke dozens of times a day still have to type the slash command each time.

Proposed solution

Either of:

• a generic action that takes an argument, e.g. { "key": "ctrl+s", "action": "command:invoke", "args": { "command": "sage" } }, or
• direct action naming, e.g. "action": "slashCommand:sage".

Chords (e.g. ctrl+k s) should work the same as for built-in actions.

Why it matters

Custom commands/agents are first-class in the docs, but they're second-class ergonomically: everything built-in can be bound to a key, everything user-defined cannot. This is also an accessibility/RSI issue — for users with hand pain, replacing repeated typed invocations with a single keystroke matters. (Companion request about surfacing custom agents in the UI filed separately.)