sce v0.4.0-pre-alpha-v2

CLI release assets

• Canonical sce archives are published as sce-v<version>-<target-triple>.tar.gz
• Per-archive SHA-256 checksum files are published as sce-v<version>-<target-triple>.tar.gz.sha256
• Combined artifact metadata is published as sce-v<version>-release-manifest.json
• Combined artifact manifest signatures are published as sce-v<version>-release-manifest.json.sig
• Combined checksums are published as sce-v<version>-SHA256SUMS
• The npm package tarball is published as sce-v<version>-npm.tgz
• Flatpak source-built packaging metadata is published as sce-v<version>-flatpak-manifest.tar.gz, with matching .sha256 and .json metadata assets; this is not a prebuilt Flatpak app or Flathub publication.
• Flatpak source-built .flatpak bundles are published as sce-v<version>-x86_64.flatpak and sce-v<version>-aarch64.flatpak, with matching .sha256 and .json metadata assets; install directly with flatpak install --user <url>.

What's Changed

• workflows: Add package-local phase references by @davidabram in #179
• workflow: Allow non-SCE helpers in SCE workflows by @davidabram in #185
• Source instance by @davidabram in #197
• Agent trace export by @davidabram in #198
• SCE trace sync by @davidabram in #200
• Fix default env by @davidabram in #204
• setup: Replace directory-level install with per-asset merge-aware install by @davidabram in #180

Full Changelog: v0.4.0-pre-alpha-v1...v0.4.0-pre-alpha-v2