auto-discover stops owning ports; PortAssignments deleted

[FAZuH]

32 — auto-discover stops owning ports; PortAssignments deleted

What to build: auto-discover no longer decides port availability locally. decide_ports becomes a pure translation of desired intent into a mapping request; all availability answers come from the natmap daemon via the NatmapOps seam. On a 409 conflict for a local ForwardRemote target, the service is still registered in Consul without the mapping (skip-but-register). The per-pass PortAssignments load/save and the local is_port_free bind-check are removed, and the now-orphaned PortAssignments type is deleted from lab-lib.

Blocked by: #31 — the daemon must be able to allocate on the mapping flow first.

Status: ready-for-agent

• decide_ports issues mapping requests to the daemon (no local availability decision); no is_port_free bind-check remains in auto-discover
• PortAssignments is no longer loaded/saved by auto-discover and the type is deleted from lab-lib (including any remaining consumers)
• 409 conflict on a local ForwardRemote target → service still registered in Consul (skip-but-register)
• sync command path and container-event path behave identically via sync_service
• Unit-tested against an in-memory NatmapOps fake configured to report conflicts; auto-discover + natmap + root lib suites green

[FAZuH]

This work is already landed on v0.2 (pointer at merge 3dc79fa). feat/c4-port-authority and feat/c5-inspection were rebased onto v0.2; every commit was a patch-equivalent already present there, so both branches linearized down to v0.2 cleanly, the tree was verified (PortAssignments absent, shared lab-lib inspect module in crates/lab-lib/src/docker.rs, both daemons consuming it), and ./dev.sh test passed 431/0. Closed by hand because the merge history does not fire a keyword from the non-default branch.