<leader>oi cannot accumulate selections across files

[jensenojs]

Problem

The current <leader>oi behavior has two issues that prevent accumulating selections across files:

1. Selections are cleared when switching files - After selecting content in File A, switching to File B clears the previous selection
2. Cannot add selections when panel is already open - When the panel is open, selecting content in another file and pressing <leader>oi has no effect

Reproduction

1. Open File A, select some code, press <leader>oi to add to context
2. Switch to File B, select another piece of code
3. Press <leader>oi - expected to add File B's selection to context, but:
   • Issue 1: If panel is not open, File A's selection is already cleared
   • Issue 2: If panel is already open, nothing happens

Expected Behavior

Allow accumulating selections across files, supporting selection in any buffer and adding to the existing selection set, with selections persisting throughout the session lifecycle.

Proposed Solution

1. New API: context.add_visual_selection() - Only adds the current visual selection without clearing existing selections
2. Bug fix: Modify debounced_load() to append selections instead of replacing them
3. New keymap: <leader>oa (add selection) specifically for adding selections, separating the responsibility from <leader>oi (open input)

This allows <leader>oa to add selections from any buffer at any time without interfering with the normal <leader>oi workflow.

[sudo-tee]

Great suggestion.

The selection was coupled to the current file in the past. Now it is not anymore, it will be a good opportunity to revise the way it works.

[sudo-tee]

@jensenojs

I created a MR that would solve both of your concerns
#261

The shortcut to add selection is <leader>oy or the command Opencode add_visual_selection

Let me know it it works for you