fix: retain all macOS open-document paths

[PathGao]

Fixes #299

macOS RunEvent::Opened handling now retains every delivered file URL, drains all startup paths in delivery order, and opens every startup document through the normal tab flow. This is a direct multi-document fix; #212 remains open for the distinct second-copy single-instance Apple Event timing problem.

Depends on #298. Please merge in this order: #286 → #287 → #288 → #293 → #296 → #298 → this PR.

Validation:

• npm run check
• npm test (133 passing)
• cargo test (20 passing)
• macOS runtime Apple Event smoke test remains required after a build.

[PathGao]

@alecdotdev This extends the same chain with a scoped macOS open-document fix. It deliberately does not claim to resolve #212’s second-bundle/single-instance timing limitation. All local checks pass; please merge after #298.