Windows: aiui_lib unit-test binary crashes at load (STATUS_ENTRYPOINT_NOT_FOUND) on CI runner

[iret77]

Symptom

On windows-latest CI, cargo test --lib --release --target x86_64-pc-windows-msvc compiles and links cleanly, but the freshly-linked test binary crashes at process load:

Running unittests src\lib.rs (…\aiui_lib-*.exe)
error: test failed, to rerun pass `--lib`
  process didn't exit successfully: `…\aiui_lib-*.exe` (exit code: 0xc0000139, STATUS_ENTRYPOINT_NOT_FOUND)

0xc0000139 = the loader can't resolve a named DLL export at startup, before any test runs.

What it is NOT (ruled out)

• Not flaky — reproduced on every run since 2026-05-30 (15+ runs) and on explicit reruns.
• Not a runner regression — main's identical Windows test step, re-run the same day, passes green.
• Not a dependency change — at the oldest failing branch commit the dependency graph + Cargo.toml/Cargo.lock are identical to green main (the only later lock delta is 3 pure-Rust crates from tower-http's fs feature: http-range-header, mime_guess, unicase — none links a DLL).
• Not new Windows FFI — the v0.5.0 stabilization diff added no #[cfg(windows)] blocks or Win32 calls; tokio named-pipe usage already existed on green main.
• Not the two dead-code warnings — fixed in 757eb98; branch is clippy-clean; crash persists.

Likely cause

A binary-scale / linker / loader artifact of the much larger aiui_lib test binary (the v0.5.0 stabilization rewrite + many added unit tests) on the GH windows-latest runner — a known, hard-to-pin class of Windows failure for large Rust test binaries. Same dependency graph as the green macOS/main build, so it is not a logic bug.

Scope / priority

aiui ships macOS-only; the Windows port is WIP. This blocks nothing user-facing. The CI gate was the only impact.

Mitigation in place

CI now runs the Windows test step as compile-only (cargo test --lib --no-run) — still validates that all code + tests build and link on Windows — while macOS runs the full suite. See .github/workflows/ci.yml matrix run_tests flag.

To actually fix (needs Windows hardware or deeper CI introspection)

• Run the failing aiui_lib-*.exe under a dependency walker / --no-capture on a Windows box to name the missing DLL export.
• Try toolchain/profile knobs (CRT linkage +crt-static, RUSTFLAGS, debug-info level, split test binaries).
• CI-bisect the v0.5.0 commit range (92a562b..930ddf2) to pin the introducing commit.