test(cli): live profile-router spawn/route/reap integration test

[FerroxLabs]

PR-7 increment 2d — live end-to-end coverage of the profile SUPERVISOR/ROUTER.

Context

The profile router (CliProfileRouter) and RosterEntry (increments 2b/2c) already shipped in #220. Its only tests were fail-closed unit checks in profile_router.rs that never spawn a child. Per Sean's FEATURE-DECISIONS ruling (core profiles must be first-class + fully tested before Hermes #66 surfacing), this closes the one real gap: a live test that exercises the whole topology.

What it does

A single hermetic integration test file (crates/wcore-cli/tests/profile_router_live.rs) driving three real processes:

test ──AcpClient/HTTP──▶ wayland-core acp serve --enable-profile-router  (supervisor)
                                   │ spawns + routes
                                   ▼
                         wayland-core acp serve --profile <name>          (child)
                                   │ engine turn
                                   ▼
                               MockLlm (POST /v1/messages)

Asserts the load-bearing behaviour of the increment:

• opening a profile:<name> session spawns exactly one dedicated child (Unix pgrep -P on the supervisor pid);
• a turn routes supervisor → child → the child's own provider and streams the reply back through both hops;
• deleting the session reaps the child;
• an unknown profile fails closed — rejected, no child spawned.

Hermetic by construction

Every process points WAYLAND_HOME/HOME at throwaway tempdirs, WAYLAND_PROFILES_ROOT is a throwaway tempdir (so the only profile in existence is the one the test seeds), the full provider-credential env set is stripped, and the mock scripts the turn — no real provider is contacted, no developer config/keys are read or mutated. Mirrors the acp_gate_d012.rs hermetic pattern.

Verification

Hetzner (Linux): nextest run -p wcore-cli --test profile_router_live → 6/6 passed, stable across 5/5 consecutive runs (~0.8s each, incl. the Unix spawn/reap pgrep assertions).

No production code change. New test file only.