Extend the existing CI workflow with an ubuntu-only "End-to-end (soulfind)"
job that builds soulfind from source (LDC + `dub build :server`), points
SOULFIND_BIN at it, and runs the e2e suite with SOULSEEK_E2E_REQUIRED=1.
Also widen the clippy job to the whole workspace.
The e2e harness gains SOULSEEK_E2E_REQUIRED: when set, a missing/unstartable
server is a hard failure instead of a silent skip, so CI genuinely exercises
the client end-to-end. Add e2e coverage for two existing behaviours a single
server can verify: wrong-password rejection and concurrent logins.
- Add check-release job to determine if a release is needed
- Build binaries in parallel for all platforms before release
- Create release and attach binaries in final step
- Start with version 0.1.0