fix(vscode): route focusChatInput (Cmd+Shift+A) to active panel (#526)

* fix(vscode): route focusChatInput (Cmd+Shift+A) to active panel

The focusChatInput command was hardcoded to always target the sidebar
KiloProvider. When the Agent Manager panel was focused, the shortcut
had no effect. Now the command checks which panel is active at
invocation time and routes the message accordingly.

* fix(vscode): route addToContext setChatBoxMessage through target() too

Both setChatBoxMessage and focusInput in the addToContext handler now
use target() so the context text and focus always go to the same panel.