[FEATURE]: Add `opencode` deep link to the desktop app

[Rettend]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

vscode has vscode://
cursor has cursor://

adding an opencode:// deep link would allow the app to be opened by other apps. it could also support opening a specific project.

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• [FEATURE]: opencode:// protocol handler to support cmds and args #6009: [FEATURE]: opencode:// protocol handler to support cmds and args
• Feature Request: Desktop app deep links (opencode://session/<id>) #6232: Feature Request: Desktop app deep links (opencode://session/)
• [FEATURE]: Deeplink support for web UI #6847: [FEATURE]: Deeplink support for web UI

Feel free to ignore if none of these address your specific case.

[Rettend]

mb looks like duplicate