Add completions menu for files and folders

[Adictya]

Demo:

• Adds completions menu for files and folders. You can press "@" to bring this up and fuzzy find any file in the working directory.

• Built to be extensible so we can add more providers for things like git, lsp symbols etc given we also build the tools.

• Adds a minimal reusable list component since I had found myself reusing a lot of code from commands dialog.

Let me know if this looks good and if the ux feels good and if its line with what you guys think this feature should look like. Also feel free to be as pedantic as you want, I want to strictly adhere to the repo coding style so if any naming/folder convention doesn't match or if any variable name is not ideal.

[adamdotdevin]

will look at this first thing today; looks great! just to be clear, there are two features at play here: the @file/folder/symbol feature is a mechanism for explicitly adding content to the context (a la cursor, and others), is this that? or is this file path completion? both are great, we'd just want to switch to having the / character initiate it if it's the latter.

[Adictya]

I modeled it more for the cursor like mechanism as you will see in the implementation, but since the view tool is able to pick up file paths just from the text it works like the latter for now. If needed I can add the file contents statically to the context as well. Whichever way you feel works best with the project. It can be / now and then when we add git or lsp support it can become @ with all the changes to ui that accompany adding another completion provider

[adamdotdevin]

@Adictya this is incredible, seriously, thank you so much for going out of your way to make the codebase better. ❤️

my only two thoughts/questions:

• bubbletea "bubbles" has a list component, does it accomplish the same thing as the simple-list component? fwiw, i'm not opposed to having this in the opencode repo, it works great, just wanted to see if you had considered using it and if there were tradeoffs.
• the @ vs / thing; i'd really like to fast follow this PR (happy to help) with a PR to enable the @ feature in whole, where you can @ a file/folder/symbol (we've got an LSP workspaceSymbols tool now that forms the basis for looking up symbols). i think having both features is where we want to land, so i'm inclined to have you switch the trigger to / for this feature, and then work on the second (@). related, i also want to have / commands as a concept, maybe replacing the command palette or supplementing; could extend this file path completion to also include commands (like claude code). all of that is outside the scope of this PR, just bringing it up for context.

[Adictya]

Hey thanks a lot @adamdottv , it was a great experience. Always a joy to simplify code.

• For the list thing, yes I did consider it I read through the source code of the list component even and the bubbletea file picker component as well and these were the first things I tried using for the dialog but its too opinionated on its styling of list elements and the feature set it provides. I then looked at how other parts of the code were doing it and concluded that this must be the reason other components opted out of it. Extremely open to suggestions if you wanna take a look and see if simple list is still better, happy to change the implementation.

• Makes sense, I can follow up with the pr for that and the command thing . And for now switch this to /.

[adamdotdevin]

on the bubbles thing, you made the right call, and i suspected their list might not be configurable enough! your version is perfect, fits the needs of the app exactly

[Adictya]

@adamdottv Changed the initiation key to '/'