fix(app): ship checksum worker sidecar across all bundle formats

[lukyrys]

What

Fixes the checksum worker not being shipped (or not discoverable) in production
bundles. Original Windows-only ZIP fix is extended to all bundle formats
(NSIS/MSI/Windows ZIP, macOS DMG/ZIP, Linux DEB/RPM/Pacman/AppImage/ZIP),
adds worker lifecycle hardening, and gates the build on cross-package tests.

Why

Bun-compiled binaries see import.meta.url as /$bunfs/root/<binary> (virtual),
so the worker URL resolved to a non-existent file. Tauri bundles also weren't
copying the worker into the resource directory. Result: silent 0% hang on
LISH creation, then segfault on stop.

The fix:

1. Worker shipped as real sidecar at <dir(execPath)>/lish/checksum-worker.js
2. bundle.resources includes the worker on all 3 platforms
3. app/build.sh ZIP/DEB/RPM staging copies the worker
4. worker.terminate() swapped for worker.unref() on Windows compiled (Bun segfault avoided)
5. Pre-build test gate runs typecheck + unit tests before producing artifacts

Verified

Platform	Build	Worker runtime
Windows backend (zip standalone)	✅	✅ smoke + stopCreate
Linux ZIP	✅ 4m on lister	✅ 16+24 chunks
Linux DEB	✅	✅ 24 chunks (extracted)
Windows Tauri NSIS	✅ 2m local	✅ 24 chunks + 3 file events
macOS / Linux Tauri	not exercised	logical only — same code path

Pre-build gate: typecheck + 405 unit tests + frontend bun run check + shared/cli typecheck.
Skip with SKIP_TESTS=1 only in emergencies.

Commits (13)

Type	Commit	Subject
fix	760eec5	ship checksum worker for windows builds
fix	4bd3606	bundle worker as Tauri resource on all platforms
fix	03e09a6	include worker in zip and linux package staging
fix	98ef61f	exit on first build step failure on windows
refactor	07f26e6	use releaseWorkers helper on success path
perf	4320673	cache compiled-binary detection at module load
style	a5de9f1	typed worker.unref intersection
style	c76e9ce	clarify messageerror description
chore	642da99	drop nsis languages without multiuser plugin coverage
test	ebdffc7	stopCreate regression test for compiled worker abort path
test	03e48d5	run typecheck and unit tests as backend pre-build gate
test	8758bed	run cross-package verification as app pre-build gate
test	9ed2471	skip windows-specific backslash traversal cases on posix

⚠️ Coordinate with PR #26

PR #26's docker/Dockerfile compiles app.ts and checksum-worker.ts with
two entry points into a single --outfile, which doesn't produce the sidecar
this PR's runtime resolution requires. Whichever PR lands second must split
the Docker build into two bun build steps mirroring backend/build.sh.

Out of scope

• Migrate to Tauri's bundle.externalBin + tauri-plugin-shell sidecar API
• Factor common bundle.resources into shared tauri.conf.json (RFC 7396 merge behavior unclear)
• DRY 3× duplicated worker build line across backend/build.{sh,bat} + app/build.bat
• FHS-compliant Linux layout (/usr/lib/libershare/ instead of /usr/bin/lish/)