BUG: Plugin keybindings can override built-in shortcuts

[andrinoff]

Describe the bug

In plugin/api.go, matcha.bind_key() appends keybindings without checking for conflicts with built-in shortcuts (d for delete, a for archive, r for reply, v for visual mode, etc.). A plugin registering a conflicting key silently breaks core functionality.

m.bindings = append(m.bindings, KeyBinding{
    Key:         key,
    Area:        area,
    Description: description,
    Fn:          fn,
})

To reproduce

1. Create a plugin that binds a built-in key:

matcha.bind_key("d", "inbox", "My plugin", function() end)

2. Install and load the plugin
3. Press d in the inbox — either the plugin or delete runs, but not both as expected

Expected behavior

Either:

• Warn the user when a plugin tries to bind a key that conflicts with a built-in shortcut
• Give built-in shortcuts priority and log a warning
• Allow users to resolve conflicts via configuration

OS

All platforms