Add Copilot instructions for CMSIS Core version sync enforcement

.github/copilot-instructions.md

@@ -0,0 +1,27 @@
+# Copilot Code Review Instructions
+
+## CMSIS Core version consistency
+
+The CMSIS Core version is defined in two places that must always be kept in sync:
+
+1. **`ARM.CMSIS.pdsc`** (repo root) — three specific `<component Cclass="CMSIS" Cgroup="CORE">` entries, each identified by its `condition` attribute:
+   - `condition="ARMv6_7_8-M Device"` → Cortex-M component (maps to `__CM_` macros)
+   - `condition="ARMv7_8-A Device"` → Cortex-A component (maps to `__CA_` macros)
+   - `condition="ARMv7-R Device"` → Cortex-R component (maps to `__CR_` macros)
+
+2. **`CMSIS/Core/Include/cmsis_version.h`** — the preprocessor defines, grouped by device profile:
+   - `__CM_CMSIS_VERSION_MAIN` / `__CM_CMSIS_VERSION_SUB` (Cortex-M)
+   - `__CA_CMSIS_VERSION_MAIN` / `__CA_CMSIS_VERSION_SUB` (Cortex-A)
+   - `__CR_CMSIS_VERSION_MAIN` / `__CR_CMSIS_VERSION_SUB` (Cortex-R)
+
+**Whenever a pull request modifies either of these files, verify that the version is consistent across both locations and remind the author to update the other location if it has not been updated.**
+
+The version check must be done per device profile (A, M, R):
+
+| `ARM.CMSIS.pdsc` component (`condition`) | `cmsis_version.h` macros |
+|---|---|
+| `Cversion` on `condition="ARMv6_7_8-M Device"` | `__CM_CMSIS_VERSION_MAIN` . `__CM_CMSIS_VERSION_SUB` |
+| `Cversion` on `condition="ARMv7_8-A Device"` | `__CA_CMSIS_VERSION_MAIN` . `__CA_CMSIS_VERSION_SUB` |
+| `Cversion` on `condition="ARMv7-R Device"` | `__CR_CMSIS_VERSION_MAIN` . `__CR_CMSIS_VERSION_SUB` |
+
+For example, if `Cversion="6.2.0"` for the `ARMv6_7_8-M Device` component, then `__CM_CMSIS_VERSION_MAIN` must be `6` and `__CM_CMSIS_VERSION_SUB` must be `2`. Each profile's version must be checked independently.