fix(firmware): define the Kconfig options this gate is guarded by

csi_collector.c guards the mesh-aligned gate on CONFIG_CSI_GATE_MESH_ALIGNED,
but nothing defined it. Upstream's Kconfig.projbuild has no such symbol and
this branch did not add one, so the #ifdef would never be true and the gate
would ship dead: present in the diff, absent from the binary, and silent about
it. The A/B this PR offers would have compared the old gate with the old gate.

Adds CSI_GATE_MESH_ALIGNED (default y, the gate) and CSI_SEQ_DIAG (default n,
the probe that measures its effect rather than assuming it).

Co-Authored-By: claude-flow <ruv@ruv.net>
Claude-Session: https://claude.ai/code/session_01BHNNWbmKvxXrVaEDwXEBNo

firmware/esp32-csi-node/main/Kconfig.projbuild

@@ -517,3 +517,20 @@ menu "Onboard LED (ADR-183)"
             colormap, in milli-units (250 = 0.25). Lower = more sensitive
             (reaches yellow with less motion).
 endmenu
+
+config CSI_GATE_MESH_ALIGNED
+    bool "Align the CSI rate gate to mesh time (enables cross-node pairing)"
+    default y
+    help
+      The per-node elapsed gate ("20 ms since MY last accept") gives every node
+      an independent phase, so two healthy nodes at 50 Hz accept disjoint
+      frames and nothing can be paired across them. This aligns the 20 ms
+      window to mesh time so nodes choose the same windows.
+
+config CSI_SEQ_DIAG
+    bool "Log (source MAC, rx_seq) for every CSI callback (ADR-345 phase 2 probe)"
+    default n
+    help
+      Diagnostic. Emits the transmitter address and 802.11 sequence number for
+      each CSI callback so the effect of the gate above can be measured rather
+      than assumed. Verbose; leave off in normal operation.