feat(qemu): ADR-062 QEMU swarm configurator for multi-ESP32 testing

YAML-driven orchestrator for testing multiple ESP32-S3 QEMU instances
with configurable topologies (star/mesh/line/ring), role-based nodes
(sensor/coordinator/gateway), and swarm-level health assertions.

New files:
- ADR-062: architecture decision record
- qemu_swarm.py: main orchestrator (1097 lines)
  - YAML config parsing with schema validation
  - 4 topology implementations with TAP/SLIRP fallback
  - Per-node NVS provisioning via provision.py --dry-run
  - Signal-safe cleanup, dry-run mode, JSON results output
- swarm_health.py: 9-assertion health oracle (653 lines)
- 7 preset configs: smoke (2n/15s), standard (3n/60s),
  large-mesh (6n/90s), line-relay (4n/60s), ring-fault (4n/75s),
  heterogeneous (5n/90s), ci-matrix (3n/30s)
- CI: swarm-test job in firmware-qemu.yml

Co-Authored-By: claude-flow <ruv@ruv.net>

scripts/swarm_presets/ring_fault.yaml

@@ -0,0 +1,41 @@
+# Ring topology with fault injection: 4 nodes, 75s
+swarm:
+  name: ring-fault
+  duration_s: 75
+  topology: ring
+  aggregator_port: 5005
+
+nodes:
+  - role: coordinator
+    node_id: 0
+    scenario: 0
+    channel: 6
+    edge_tier: 2
+    is_gateway: true
+
+  - role: sensor
+    node_id: 1
+    scenario: 1
+    channel: 6
+    tdm_slot: 1
+
+  - role: sensor
+    node_id: 2
+    scenario: 2
+    channel: 6
+    tdm_slot: 2
+
+  - role: sensor
+    node_id: 3
+    scenario: 3
+    channel: 6
+    tdm_slot: 3
+
+assertions:
+  - all_nodes_boot
+  - no_crashes
+  - tdm_no_collision
+  - all_nodes_produce_frames
+  - coordinator_receives_from_all
+  - no_heap_errors
+  - max_boot_time_s: 12