docs: migration guide to v3

.gitignore

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 .github/copilot-instructions.md
 *.md
 !README.md
+!migration-guide.md
 *.yaml
 !config.yaml

migration-guide.md

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+# 🚨 Breaking Change Release — v3.0.0
+
+## 🔑 Breaking Changes
+
+### 1. Explicit flag syntax
+
+* **Long-form flags** must now use `--` (e.g., `--profile`).
+* **Short-form flags** must now use `-` (e.g., `-p`).
+
+---
+
+### 2. `config` now means “application configuration”
+
+* `config` now refers to the **application’s own configuration** (Go-standard).
+* `configv2` has been **removed**.
+
+---
+
+### 3. Old `config` → now called `profile`
+
+* The concept of `config` used for provisioning (previously passed as `configv2`) is now called a **profile**.
+* Use the `--profile` flag to provide this, aligning with the rest of the device-management-toolkit.
+
+---
+
+## 🚀 Migration Examples
+
+### Example: Switching from `configv2` to `--profile`
+
+**Before (v2.x):**
+
+```bash
+rpc-go configure --configv2 path/to/profile.yaml
+```
+
+**After (v3.0):**
+
+```bash
+rpc-go configure --profile path/to/profile.yaml
+# or, where supported:
+rpc-go configure -p path/to/profile.yaml
+```
+
+
+
+## ✅ Summary
+
+* **Flags must be explicit** (`--long`, `-s`).
+* **`config` = app configuration**.
+* **`configv2` removed**.
+* **`--profile` replaces `configv2`**.
+
+---
+