[FEATURE] chat:insetSequence Chat action keybinding

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

I would like the ability to bind key sequences to unicode characters, newlines, etc. I find the current mechanisms of largely having to copy-paste in these situations as way less economical than other apps I use. It also forces me our of Claude Code and into other tools.

Proposed Solution

create an action in the chat contest of keybindings, with a similar pattern to chat:insertSequence('...').

Alternative Solutions

There are many alternatives to the string "insertSequence", maybe insertString, insertChar, insertRune, etc. It's mostly important that it matches what the input is.

Priority

High - Significant impact on productivity

Feature Category

Configuration and settings

Use Case Example

```keybindings.json
{
"$schema": ...
"$docs": ...
"bindings": [ {
"context": "Chat",
"bindings": {
"ctrl+y": "chat:insertSequence('✅')",
"enter": "chat:insertSequence('\n')"
}
} ]
}

### Additional Context

_No response_