Windows: integration failures

[arg1998]

The integration suite fails on windows-latest (first CI run, PR #1). The job runs with continue-on-error until these are fixed.

Failing tests:

• single port: the browserhive executable › spawn bin --admin --auth token → banner → /health ready → MCP list_sessions → SIGTERM exits 0 — exit code after SIGTERM is not 0 (Windows has no SIGTERM semantics for child processes).
• auth-state save + restore (real Chromium) › full-profile save through the tool and restore — INTERNAL_ERROR from save_full_profile.
• observability end-to-end (real Chromium + SQLite) › projects a full session lifecycle into the database; validation failures are recorded rows too.
• performance under load (real Chromium) › 10 parallel isolated sessions — timed out at 10 s.
• vault_fill end to end (fake bw + real Chromium) › unlock through the fake bw — VAULT_UNLOCK_FAILED (the fake bw is a Bun script with a shebang; Windows cannot execute it directly).

Log: https://github.com/arg1998/BrowserHive/actions/runs/35155988311/job/104995409678