Respect custom Cargo target directories

[Bortlesboat]

Summary

• resolve build artifact lookup through CARGO_TARGET_DIR when it is set
• keep the default src-tauri/target lookup unchanged when the env var is absent
• cover the Windows MSI and raw-binary copy paths that currently still look under the default target dir after a short-dir build
• rebuild dist/cli.js from the TypeScript source change

Refs #1230

Testing

• RED: pnpm exec vitest run tests/unit/base-builder.test.ts failed on the new CARGO_TARGET_DIR Windows artifact path assertion before the fix
• pnpm exec vitest run tests/unit/base-builder.test.ts
• pnpm exec vitest run
• pnpm run cli:build
• pnpm exec prettier --check bin/builders/BaseBuilder.ts bin/builders/LinuxBuilder.ts bin/builders/MacBuilder.ts bin/builders/WinBuilder.ts tests/unit/base-builder.test.ts
• git diff --check

[tw93]

@Bortlesboat thank you for the PR. I added one small follow-up so WinBuilder uses Windows binary names even when the test host is not Windows, then merged this into main.

The post-merge Quality & Testing run is green, and the fix will be included in the next release.