- Check $LASTEXITCODE after bun install and bun build in install.ps1
- Use -Encoding OEM for .cmd shims to preserve non-ASCII paths
- Use -Encoding UTF8 for built script with shebang
- Distinguish "not found on PATH" from "health check failed"
- Add fail-fast: false to CI matrix for independent OS results
- Fix stale comments: close() docstring, HOME references, CRLF note
- Add Windows sections to Chinese README and CONTRIBUTING.md
- Fix ambiguous "Both" wording in README prerequisites

- Merge prerequisites inline with installation heading
- Share git clone step, split into Linux/macOS and Windows subheadings
- Apply same structure to Chinese README

- Add extensionless bash shim alongside .cmd for Git Bash/MSYS2 compat
- Fall back to copy when symlinks fail (no Developer Mode)
- Use system default encoding for .cmd shims (locale-safe)
- Add spawnSync timeout to CLI tests (prevents hang when codex installed)
- Fix protocol test race: use local clients instead of shared afterEach
- Show only first result from 'where' in health check output
- Add installer smoke tests to CI for both platforms

On Windows, bun:test's expect(promise).rejects.toThrow() prevents the
event loop from reaching the I/O phase needed to flush Bun's FileSink
stdin buffer, causing request timeouts in tests 4 and 5.

Replace the four affected assertions with a captureErrorMessage() helper
that uses plain await (matching how production callers use the client),
which flushes correctly.

Also fix install.ps1 to write bash shims without a UTF-8 BOM using
[System.IO.File]::WriteAllText with UTF8Encoding($false), replacing
Set-Content -Encoding UTF8 which emits a BOM in PowerShell 5.1 and
breaks shebang recognition.

The bash wrapper script in install.ps1 used #!/usr/bin/env bun but
contained bash syntax (exec bun ...), causing Git Bash to pass it
to Bun which failed to parse it as JavaScript. Fixed both dev-mode
and build-mode shims to use #!/usr/bin/env bash.

- Log warnings on proc.kill() and taskkill failures instead of empty catches
- Check taskkill exit status via stdio: pipe
- Harden captureErrorMessage test helper to throw on unexpected resolve
- Wrap bun build in try/catch consistent with bun install
- Exit 1 when codex-collab health fails in installer

taskkill returns status null when the process is already dead (killed
by proc.kill()). Add null to the skip condition so this expected case
doesn't produce a noisy warning during health checks.

P1: Swap kill order in close() — run taskkill /T /F first to kill the
process tree, then proc.kill() as fallback. Previous order killed the
direct child first, removing the PID that taskkill needs to traverse
the tree when codex is invoked via a .cmd wrapper.

P2: Use UTF-8 encoding for .cmd shims instead of ASCII. ASCII encoding
corrupts non-ASCII path segments (e.g. Chinese directory names),
breaking dev installs in those locations.

Avoids spurious "rollout" warnings from the Codex app-server when
killing a thread that was already killed or archived. Instead of
suppressing the errors, check local status in threads.json first
and early-exit if the thread is already marked as killed.