feat: allow enable/disable codebase indexing via settings.json

[tmeckel]

Currently it's only possible to enable or disable codebase indexing via the UI of the extension. And it's a global setting, i.e it's either on or off for every workspace.

I propose to introduce a setting kilo-code.codebase-indexing with the values enabled, disabled (or true, false). With that it would be possible to selectively enable or disable codebase indexing for a workspace.

[alefteris]

For anyone else looking for this, here is how to configure at the repo level:

File: <repo root>/.kilocode/config.json

{
	"project": {
		"managedIndexingEnabled": false
	}
}

Docs: https://kilo.ai/docs/advanced-usage/managed-indexing#how-to-enable