Cmd+click on local file paths opens wrong URL (http instead of file://) #19144

Bug Description
When cmd+clicking on a local file path (e.g., README.md, src/app.ts) in a chat message, OpenCode tries to open it as an HTTP URL instead of a local file.

Steps to Reproduce

1. Have a project open in OpenCode Desktop
2. Send/receive a message containing a local file path like README.md
3. Cmd+click on the file path
4. See error: "Unable to connect. Is the computer able to access the URL?"

Expected Behavior
Local file paths should open using the file:// scheme, which opens the file in the default application (e.g., mkdn for .md files).

Root Cause
In packages/desktop-electron/src/main/ipc.ts, the open-link handler passes bare file paths directly to shell.openExternal(), which treats them as HTTP URLs.

Fix
Convert bare file paths (those without a scheme like http://, file://, etc.) to file:// URLs with resolved absolute paths before calling shell.openExternal().

Testing

• Verified that clicking README.md now opens in the default markdown viewer (mkdn)
• Verified that file://, https://, and other schemes still work correctly