feat: Scope3 SDK v2.0.0 - Persona-based API rebuild

.changeset/sdk-v2-rebuild.md

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+---
+"scope3": major
+---
+
+SDK v2.0.0: Persona-based API architecture
+
+Complete rebuild of the Scope3 SDK with persona-based design for the Agentic Platform v2 API.
+
+**New Features:**
+- Unified `Scope3Client` with `persona` parameter: `buyer`, `brand`, or `partner`
+- Full CLI with `scope3` command for all API operations
+- REST and MCP adapter support
+- Chained resource access: `client.advertisers.brand(id).link()`
+
+**CLI Highlights:**
+- `scope3 config set apiKey <key>` - persistent configuration
+- `scope3 commands` - list all available commands by persona
+- Table, JSON, and YAML output formats
+- Environment support: production and staging
+
+**Breaking Changes:**
+- Removed `Scope3AgenticClient` - use `Scope3Client` with `persona` parameter
+- Removed auto-generated types from OpenAPI (now manually maintained)
+- New API surface matches Agentic Platform v2
+
+**Migration Guide:**
+
+```typescript
+// Before (v1):
+import { Scope3AgenticClient } from 'scope3';
+const client = new Scope3AgenticClient({ apiKey: '...' });
+
+// After (v2):
+import { Scope3Client } from 'scope3';
+
+// For buyers (advertisers, campaigns, bundles):
+const buyerClient = new Scope3Client({ apiKey: '...', persona: 'buyer' });
+
+// For brand owners:
+const brandClient = new Scope3Client({ apiKey: '...', persona: 'brand' });
+
+// For partners (DSPs, publishers):
+const partnerClient = new Scope3Client({ apiKey: '...', persona: 'partner' });
+```
+
+**Testing:**
+- 225 tests passing
+- Verified with real API calls to staging environment
+- CLI tested for all major workflows