feat(engine): dynamic min-cut mesh partition guard (ruvector-mincut)

Maintains an exact min-cut over the live mesh coupling graph — nodes are
sensing nodes, coupling is the product of fusion attention weights — and
surfaces per cycle, as TrustedOutput::mesh:

- cut value: the global "how close is the array to partitioning" number,
  a structural measure per-node heuristics miss;
- weak side: which specific nodes would split off (failure/jamming triage,
  feeds ADR-032 posture);
- at-risk flag: counts as a structural event for the drift->recalibration
  advisor (alongside ADR-142 change-points).

Degenerate cases fail toward risk: a node with zero coupling is reported as
already partitioned (cut 0, that node as the weak side).

Measured cost policy (criterion, 12-node mesh — the honest part):
- weights quantized (1/64) + change-gated: steady-state cycles do ZERO graph
  work and reuse the cached cut (~7.3 us, ~23x cheaper than building);
- on any real change a full exact rebuild (~171 us) is used, because ONE
  DynamicMinCut delete+insert measured ~240 us — the subpolynomial machinery
  amortizes on much larger graphs, so rebuild-on-change is the measured
  optimum at mesh scale (one-edge case -28% after switching policy);
- full process_cycle with the guard: ~33 us for 4 nodes vs the 50 ms budget.

9 mesh_guard tests (weak-node detection, steady-state zero updates,
sub-quantum gating, join/drop rebuild, determinism, disconnection) + an
engine-level wiring test (down-weighted node -> weak side -> recalibration).
Engine 24 tests; workspace gate 2,946 passed / 0 failed.

https://claude.ai/code/session_01MjBucx95K4BuUxZi8NWwRH

v2/Cargo.lock

@@ -10910,6 +10910,7 @@ version = "0.3.0"
 dependencies = [
  "blake3",
  "criterion",
+ "ruvector-mincut",
  "wifi-densepose-bfld",
  "wifi-densepose-core",
  "wifi-densepose-geo",