[Feature]: Open project by dragging a Finder folder onto the dock icon

[stickerdaniel]

Before submitting

• I searched existing issues and did not find a duplicate.
• I am describing a concrete problem or use case, not just a vague idea.

Area

apps/desktop

Problem or use case

Dragging a folder from Finder onto the T3 Code dock icon does nothing. The Electron main process (apps/desktop/src/main.ts) has no app.on('open-file') handler. This means both macOS folder-drop and t3code CLI workflows are unsupported.

Proposed solution

• Register app.on('open-file') in the main process, buffering paths received before app.whenReady()
• Add requestSingleInstanceLock() + second-instance handler so a running instance receives the path instead of spawning a duplicate
• Send the opened path to the renderer via a new IPC channel (e.g. desktop: open-folder-path )
• Web app receives the path and creates/switches to the matching project
• Parse process. argv for a folder path on first launch (covers t3code /some/folder )
• Update Electron builder config to declare folder association via CFBundleDocumentTypes / Info.plist

Why this matters

Dragging a folder onto a dock icon is a core macOS interaction pattern. Not supporting it makes the app feel incomplete. This also unblocks the CLI open workflow requested in #517

Smallest useful scope

macOS only, handle open-file for directories and navigate to the project. CLI args and second-instance forwarding can follow separately.

Alternatives considered

Currently the only way to add a project is through the in-app folder picker dialog. #517 requests the CLI side of the same problem.

Risks or tradeoffs

Need to handle the case where the dropped path is not yet a registered project by auto-adding it. Also need to decide behaviour when the app is not yet fully bootstrapped (buffer the path and flush after ready).

Examples or references

VS Code: code . / drag folder onto dock icon
Ghostty: drag folder onto dock icon to open terminal in this path

Contribution

• I would be open to helping implement this.