feat: add configurable paste summary thresholds

[kennyfrc]

What this does

• Adds configurable paste summary thresholds under experimental.editor.summary_thresholds
• Allows users to customize when pasted text gets converted
• Maintains current default of 3 lines / 150 characters

Use Case

I use a lot of speech-to-text when programming with OpenCode. Oftentimes, the generated text exceeds the 150 character default, leading it to be truncated. That can be a problem as I might need to do some minor edits on the pasted text.

Configuration Example

{
  "experimental": {
    "editor": {
      "summary_thresholds": {
        "lines": 8,
        "chars": 1024
      }
    }
  }
}