feat(chat): add plan fold for outputting the current state of plans

[cenk1cenk2]

Description

At somepoint this was a feature request where, we would have plan updates and thanks to the new structure I think it works perfectly just as a thinking block.

Notes

• I have messed up with the icon mechanism a bit to be able to reuse it, it does not get everything fully from the config still reuses stuff but leaves room for extension.
• This also caused ambiguity where it now renames the existing icon_info to make it specific to tool_icon where we now can have additional icons.
• I was a bit indifferent of reusing the reasoning treesitter parser, just to comply just created somewhat of a copy with ai.

AI Usage

• Claude Opus 4.6 - I was going to do the boilerplate but it had so good of an example with the thinking block, it just copied the whole thing which looks quite good tbh, then manually moved things around to match what I would like to do API wise and reusing the functionality.

Related Issue(s)

Screenshots

Checklist

• I've read the contributing guidelines and have adhered to them in this PR
• I confirm that this PR has been majority created by me, and not AI (unless stated in the "AI Usage" section above)
• I've run make all to ensure docs are generated, tests pass and StyLua has formatted the code
• (optional) I've added test coverage for this fix/feature
• (optional) I've updated the README and/or relevant docs pages