ci: add typecheck step before desktop build to fail fast

[NewCoder3294]

Summary

• Adds a new typecheck job to the desktop build workflow that runs tsc --noEmit before any platform builds begin
• The build-tauri matrix jobs now depend on this typecheck job via needs: typecheck, so all 5 platform builds are gated behind the type check passing
• The typecheck job runs on ubuntu-latest with a 5-minute timeout, keeping it lightweight and fast

Motivation

The desktop build workflow runs a 30+ minute Tauri build across 5 platforms (2 macOS, 1 Windows, 2 Linux). If there is a TypeScript type error, developers currently have to wait for the full build to fail before discovering it. By adding a quick typecheck step that runs first, type errors are caught in under 2 minutes instead of 30+, saving significant CI time and developer frustration.

Test plan

• Verify the workflow YAML is valid (no syntax errors)
• Confirm typecheck job runs before build-tauri jobs in the workflow graph
• Confirm that a type error would cause the typecheck job to fail and skip all build-tauri jobs

🤖 Generated with Claude Code

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