fix(ci): harden macOS package retries

[GCWing]

Summary

• detect a freshly rebuilt macOS app from its executable when the cached .app directory keeps an old timestamp
• retry the Tauri packaging/signing boundary up to three total attempts with bounded 10/20-second backoff
• keep compile failures outside the retry boundary and add regression coverage for restored bundle metadata

Failure addressed

The beta.2 macOS x64 build compiled successfully, then codesign failed on the temporary OpenBitFun.zip with A timestamp was expected but was not found. The existing retry did not run because it only checked the cached .app root directory timestamp.

https://github.com/GCWing/BitFun/actions/runs/34030822805/job/101479906567

Verification

• node --test scripts/desktop-tauri-build.test.mjs (18 passed)
• git diff --check
• pnpm run test:release-packaging reached 43 passing tests; the unrelated brand-assets test could not load sharp because this isolated worktree has no node_modules