Complete Phase 12 dual-stack networking

Add IPv6-aware Wi-Fi state, HTTPS/SSH listeners, mDNS service
reconciliation, and browser Wi-Fi administration.

Include a guarded build-local fix for mDNS 1.12.0 membership handling,
focused regression suites, and Phase 12 acceptance documentation.

docs/agent/design-decisions.md

@@ -144,13 +144,13 @@ Only constraints supported by implementation or current project documentation be
 
 ## Wi-Fi callbacks enqueue; the manager owns policy
 
-**Decision:** ESP event callbacks copy bounded event data into the Wi-Fi manager queue. A permanent manager task performs driver operations, profile/AP policy, deadlines, reconciliation, and station mDNS announcement transitions. mDNS initializes at most once, remains allocated across transient disconnects while its component handlers withdraw/re-enable the STA interface, and treats failure as nonfatal.
+**Decision:** ESP event callbacks copy bounded event data into the Wi-Fi manager queue. A permanent manager task performs driver operations, profile/AP policy, deadlines, reconciliation, and station mDNS announcement transitions. mDNS initializes at most once, remains allocated across transient disconnects, and treats failure as nonfatal. IPv4 or preferred IPv6 including link-local-only establishes ONLINE; route/Internet reachability is not implied. Full DHCP hostname storage and IPv6 state access belong to TCP/IP context. HTTPS/SSH owners only publish availability with short critical sections; Wi-Fi owns DNS-SD record and family reconciliation. Public mDNS actions are not acknowledged, so absent-family disables repeat every pass and healthy enables re-probe on a slower 30-second repair cadence. Record/address withdrawal is eventual, and upstream AAAA includes deprecated-but-valid addresses.
 
 **Rationale/evidence:** Callback paths avoid blocking, NVS, and policy work. Manager deadlines consult authoritative driver/netif state so dropped events are recoverable.
 
 **Consequence for future changes:** Keep callbacks short and nonblocking. Add state transitions to the manager rather than directly invoking Wi-Fi policy from consoles, UI, or callbacks. Preserve queue-drop observability.
 
-**Relevant files:** `src/wifi_manager.{h,c}`, `src/wifi_config.{h,c}`, `src/mdns_service.{h,c}`, `src/mdns_config.{h,c}`
+**Relevant files:** `src/wifi_manager.{h,c}`, `src/wifi_config.{h,c}`, `src/mdns_service.{h,c}`, `src/mdns_config.{h,c}`. `cmake/mdns_membership.*` is a narrowly reviewed exception for mDNS 1.12.0 multicast join/leave imbalance: patch only a build-local networking source with strict version/hash guards, never the managed source. Dependency upgrades must review/remove the overlay; do not bypass its guards or restore the abandoned Phase 9 patches.
 
 ## Optional local UI cannot become a core dependency