feat: Open workspace folder in Zed (parity with VS Code)

[ChristianLuciani]

Problem

The workspace Open project folder control supports VS Code, Terminal, and File Explorer only. Users who edit in Zed must open the project folder manually after agents change files.

Proposal

Add Zed as an optional open-with target (same product surface as VS Code):

• Detect install (zed on PATH and/or platform app/CLI paths; same idea as VS Code detection)
• Show the option only when installed
• Open the conversation workspace folder via existing shell APIs
  (POST /api/shell/check-tool-installed, POST /api/shell/open-folder-with with tool: "zed")

Implementation sketch (atomic PRs)

1. AionCore — extend ToolType + ShellService detect/open for Zed
2. AionUi — WorkspaceOpenButton + i18n + IPC union type

I am happy to open draft PRs linked to this issue.

Non-goals

• Not adding Zed as an ACP agent (Zed is an ACP client, like AionUi)
• Not embedding Zed or changing the agent selector
• Not making Zed the default editor
• Not implementing a full custom-editor registry in this first change

Design question for maintainers

Is Zed-only parity acceptable for this PR series?

If you would rather invest in a generic open-with list (VS Code, Zed, Cursor, user-defined command) instead of one-off editor keys, say so and we can:

• either reshape this work into that design, or
• ship Zed-only now and treat generic open-list as a follow-up issue.

Default plan if no preference: ship Zed-only (smallest change, mirrors current VS Code path).

Related

• Prior shell/open-workspace work on Windows: fix(shell): spawn EINVAL when opening workspace folder on Windows #2210 (fix(shell): spawn EINVAL when opening workspace folder on Windows) — we will follow the robust spawn/detection patterns already in AionCore so Zed on Windows does not reintroduce .cmd / spawn EINVAL issues.
• No existing feature request for “Open in Zed” found at time of writing (2026-07-24).

Why this fits AionUi

AionUi is the cowork host; the user’s IDE is where they deeply navigate code. “Open in VS Code” already encodes that handoff. Zed is the same category of user preference—not a competing agent product.

Environment notes (for implementers)

• Desktop Electron only (button already hidden in WebUI)
• macOS / Windows / Linux best-effort detection; hide when not installed

[ChristianLuciani]

Draft implementation PRs (atomic split):

1. AionCore (shell API): feat(shell): open workspace folders in Zed when installed AionCore#685
2. AionUi (UI + i18n): feat(agent): show backend-selected thought level #3734

Both are draft until CI is green. Default implementation is Zed-only open-with parity; happy to reshape if maintainers prefer a generic open-list (see design question above).

[ChristianLuciani]

Correction: the AionUi draft PR is #3736 (not 3734).

• AionCore: feat(shell): open workspace folders in Zed when installed AionCore#685
• AionUi: feat(workspace): open project folder in Zed when installed #3736