Remove the retired applications, asset-specific libraries and DJ pack tool
from Makepad, together with their workspace and launcher entries. All 981
removed source paths are accounted for in the private Stage repository.
Keep public AI chat generation through the AI Hub's generic job runner.
Extract shared SHA-256 and UDP binding into core_util so the public hub and
model crates no longer depend on the relocated asset libraries. Preserve
the retained public coverage in the split wasm validation script.
Validation on the exact cleanup tree in an isolated checkout:
- Release checks: core_util, model, aichat, WM and Builder.
- Release builds: aichat, WM and Builder.
- Existing tests: core_util 5, model 30, aichat 7, Builder 2 passed.
- Core/model checks: wasm32, Linux and Windows passed.
- No warnings in the successful checks, builds or tests.
Known baseline: WM library tests do not compile because the unchanged
style-transition assertion compares seven expected weights with eight.
The unrelated working-tree correction is intentionally outside this commit.
