# Slice K0 portability boundary closeout

## Outcome

K0 completed at `aada8a37c1e933f9f0a3f41dc4f05615b01023bc`.
The repository now has a dedicated `AcDream.Headless` executable and matching
test project. The executable references only `AcDream.Runtime`; its transitive
closure contains no App, UI, Silk.NET, OpenAL, Arch, ImGui, renderer, audio, or
native-window assembly.

Exact rollback:

```text
git revert aada8a37c1e933f9f0a3f41dc4f05615b01023bc
```

## Boundary

- `--help` runs without constructing Runtime or loading presentation code.
- `validate --config <path>` performs strict, case-sensitive, versioned JSON
  validation without connecting.
- Unknown properties, missing required fields, duplicate/empty session IDs,
  unsupported versions, malformed files, and secret-shaped unknown fields fail
  with deterministic exit codes.
- Arbitrary command arguments and secret values are not reflected into
  diagnostics.
- Project, dependency-manifest, and loaded-assembly tests enforce the boundary.
- Runtime's existing dependency-project test now resolves MSBuild paths on
  Windows and Linux and remains valid under isolated artifact roots.

## CI and local Linux proof

`.github/workflows/headless-portability.yml` runs on Windows and Ubuntu. It
builds Plugin.Abstractions, Core, Core.Net, Content, Runtime, and Headless,
then tests only the presentation-free Core.Net, Content, Runtime, and Headless
closures. Historical `AcDream.Core.Tests` App-integration fixtures remain in
the complete-solution lane and are deliberately excluded from the no-App
restore lane.

Local Ubuntu 24.04 / .NET 10.0.302 evidence:

- Plugin.Abstractions and Core build: pass.
- Core.Net tests: 600/600.
- Content tests: 119/119.
- Runtime tests: 395/395.
- Headless tests: 12/12.
- Headless `--help`: exit 0.

Exact Windows Release evidence:

- solution build: pass (17 pre-existing Core-test warnings);
- complete solution: 8,708 pass / 5 intentional skips;
- Headless tests: 12/12;
- Runtime tests: 395/395.

## Audit

- Windows-only UDP reset handling was already guarded by
  `OperatingSystem.IsWindows()`.
- CP-1252 registration is BCL/provider-based and Linux-safe.
- immutable pak reading uses portable read-only memory mapping.
- remaining wall-clock and diagnostic-call-site cleanup belongs to K2 timing
  ownership, not the K0 process boundary.
- no retail gameplay behavior changed and no divergence row was added.