feat: publish FreeRTOS C FC09 card

README.md

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+# FC09 — Event Groups and multi-event synchronization
+
+This deterministic card implements two distinct protocols on one genuine
+FreeRTOS EventGroup:
+
+1. a priority-3 coordinator waits for **ALL** independent readiness bits;
+2. coordinator, worker A and worker B cross a three-party
+   `xEventGroupSync()` barrier.
+
+READY (`0x01`, `0x02`) and SYNC (`0x10`, `0x20`, `0x40`) masks are disjoint.
+The partial mask cannot release either protocol. Every participant receives a
+return value containing `SYNC_ALL`, while the group value becomes zero after
+the barrier's automatic clear.
+
+```sh
+make task1 host-test check-abi sim check-determinism
+```
+
+The test links upstream FreeRTOS V11.3.0 `event_groups.c`, uses finite
+timeouts, records eleven commit-last events and prints a stable digest from
+three clean Hazard3 processes.
+
+Interactive views: A2 structure, A4 participant topology, A5 execution flow,
+A6 mask/state machine, A7 runtime evidence and A8 synchronization patterns.
+
+Source basis: FreeRTOS Kernel Book, Chapter 9.