Support Windows distribution build and cross-Linux CI smoke

[plajjan]

Summary

• Build the Acton distribution on Windows with make, including Windows executable suffixes, Stack/GHC UTF-8 setup, Windows Zig extraction, and a Windows LMDB bdep for the compiler build.
• Make the Windows compiler path able to compile examples/helloworld.act to the default Linux target.
• Add CI where Windows builds the dist and produces a Linux ELF, then Ubuntu downloads and runs it.

Validation

• Windows VM: make clean && make completed successfully.
• Windows VM: dist/bin/acton.exe --help works.
• Windows VM: dist/bin/acton.exe --tempdir ... examples/helloworld.act produced a Linux ELF.
• Linux host: the Windows-built Linux ELF was verified with file/readelf and printed Hello, world!.
• Linux local: make clean && make -j2 completed successfully.
• Linux local: rebuilt dist/bin/acton --tempdir ... helloworld.act produced an ELF and it printed Hello, world!.
• Linux local: make dist/bin/acton completed successfully after the merge.
• Linux local: make test passed.
• GitHub Actions: earlier test-windows/Windows-built Linux ELF smoke passed on this branch; fresh checks are running after merging main.
• git diff --check and workflow YAML parse passed.

Notes

• actondb.exe is still left out of the Windows distribution for now; that backend C portability issue is separate.
• During manual testing, Windows OpenSSH scp truncated extensionless ELF files. The CI test uses artifact upload/download instead and verifies the ELF before running it.