aircon rig: both units, both firmwares, and the catches that blocked control

The panel now carries one wfrac node per unit, polling as well as commanding,
so a command can be checked against the unit's own answer rather than assumed.

Three things kept a panel from driving the old unit. The seeded commands catch
is off by default, which is the usual reason a fresh panel looks dead;
AIRCON_COMMANDS=1 arms it at seed time. A unit that is off names no mode, and
a flow redelivers every bound port on each run, so that rejected value blocked
every command including power-on. And the old firmware serves one connection
at a time.

ROADMAP.md

@@ -101,6 +101,18 @@ external interfaces. See `docs/architecture/structure.canvas` → *Backend – M
       that gets updated costs one retry rather than a reconfiguration. The
       payload is identical across both, so only the transport moved. Verified
       against one unit of each generation, read and command
+- [x] The aircon rig covers both units and both firmware generations: one
+      `wfrac` node each in `aircon_control`, polling as well as commanding, so
+      the panel shows what a unit answers next to what was asked of it. Three
+      things had to be fixed before a panel could actually drive one. The
+      seeded `commands` catch is off, which is the usual reason a fresh panel
+      looks dead — `AIRCON_COMMANDS=1` arms it at seed time. A unit that is off
+      names no mode and reports `unknown`, and a flow redelivers every bound
+      port on each run, so rejecting it made an idle unit impossible to start;
+      it now travels through untouched. And the old firmware serves one
+      connection at a time, answering an overlapping request with 501 — the
+      connector serialises per adapter and retries a busy one, which it must,
+      because other clients on the network are outside that lock
 - [x] Node lifecycle as a protocol (`start`/`stop`/`report_health` on `Node`),
       replacing the controller's per-type isinstance chains — the same hooks a
       connector implements, validated on the built-in nodes first