Deep links: open a specific task in the UI from external tools

[sworgkh]

Summary

There's currently no way to open a specific dev-3.0 task in the UI from outside the app. External tools can reference a task, but they can't bring you into dev-3.0 focused on it.

Motivation

Integrations like a PR dashboard can show a dev3 task badge, but it's info-only — there's no action that jumps you into the app on that task. A deep link would let any external tool (PR dashboards, scripts, notifications, docs) link straight to the right task and have dev-3.0 open and navigate to it.

Proposed feature

Support "open this task in the UI" from external callers, ideally via one or more of:

• A dev3://task/<id> URL scheme — clickable links that focus the app on a task.
• A CLI command (e.g. dev3 task open <id>) that tells the running app to navigate to a task.
• Optionally, a shareable URL in dev3 remote browser mode (e.g. ?task=<id>).

The app should raise/focus itself and navigate to the task, honoring the existing "split vs fullscreen" open-mode preference.

Notes from a quick look

A few things that suggest this is a fairly natural fit (no deep implementation detail):

• The app already navigates to a task internally when you click through a notification, so the "go to this task" behavior largely exists and could be reused.
• Electrobun supports custom URL schemes and an open-url event, so a dev3:// scheme looks feasible on macOS.
• The CLI already communicates with the running app over a local socket, so a dev3 task open <id> command (working in both desktop and remote mode) would slot in naturally.