What?

Fixes an issue where the Next.js error overlay fails to open VSCodium on macOS.

Why?

1. VSCodium renamed its macOS binary from Electron to VSCodium. COMMON_EDITORS_MACOS was only checking for the old path, causing guessEditor() to fail silently.
2. Even if launched, the editor basename codium was missing from the switch statement in getArgumentsForLineNumber, causing it to drop the line and column targeting arguments.

How?

• Added the updated VSCodium macOS binary path to COMMON_EDITORS_MACOS (and updated the legacy Electron mapping to point to codium).
• Added case 'codium': to the VS Code family block in getArgumentsForLineNumber.
• Exported the utility functions to author isolated Jest tests verifying the macOS fallback logic.

Testing Status:

• ✅ Unit tests passed locally.
• ✅ Added launch-editor.test.ts to strictly cover the codium mapping and macOS execution paths.
• ⚠️ Needs macOS Verification: I am submitting this from a Linux environment. While the unit tests pass, I am opening this as a draft so a maintainer or community member on macOS can pull this branch and verify the physical editor launch from the browser overlay before merging.

Fixes #94077