[hardware] add FlowChain hardware signal fixtures

fixtures/hardware/README.md

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+# Hardware Fixtures
+
+Last updated: 2026-05-13
+
+This folder contains local-alpha hardware projections that can be consumed by dashboard, workbench, or control-plane code without depending on live FlowRouter hardware.
+
+## Fixtures
+
+- `flowrouter_local_alpha_seed42.json`: deterministic FlowRouter-to-FlowChain operator signal projection generated from `hardware/fixtures/flowrouter_sample_seed42.json`.
+
+## Shape
+
+The fixture is a `flowmemory.hardware_operator_signals.local_alpha.v0` document. It includes:
+
+- `signalEnvelopes`: one envelope for heartbeat, receipt relay, verifier digest relay, offline alert/challenge input, and NFC memory cartridge metadata.
+- `hardwareSignals`: direct workbench/control-plane signal records for the same five envelopes.
+- `hardwareNodes`, `workReceipts`, `verifierReports`, `artifactCommitments`, `memoryCells`, `challenges`, `finalityReceipts`, and `alerts`: control-plane-friendly local fixture collections.
+- `workbenchRecords`: ready-to-render records grouped by workbench section keys, including `hardwareSignals`.
+- `boundary`: explicit local-only, advisory, optional-hardware limitations.
+
+## Validation
+
+```powershell
+python hardware/simulator/flowrouter_sim.py --validate-operator-file fixtures/hardware/flowrouter_local_alpha_seed42.json
+```
+
+These fixtures are local-only and advisory. They do not prove hardware trustlessness, production field deployment, or receipt/verifier finality.