docs: add Agent Guard branding to SDK docs and navigation (#23)

Mirror the MCP Guard naming pattern across documentation:
- Home page: 'CapiscIO SDK' → 'Agent Guard' in product stack cards
- Nav sidebar: 'CapiscIO SDK' → 'Agent Guard' in Reference section
- SDK reference index: update title and description with Agent Guard name
- All class names (SimpleGuard, CapiscioMiddleware) remain unchanged

Author: beonde

docs/index.md

@@ -90,18 +90,18 @@ Three products that work together to secure the agent economy:
 
     [:octicons-arrow-right-24: CLI Reference](reference/cli/index.md)
 
--   :material-language-python:{ .lg .middle } **CapiscIO SDK**
+-   :material-language-python:{ .lg .middle } **Agent Guard**
 
     ---
 
-    **Runtime security** — Sign requests, verify badges, enforce trust in your code.
+    **Runtime security** — Sign requests, verify badges, enforce trust in your A2A agents.
 
     ```python
     from capiscio_sdk import SimpleGuard
     guard = SimpleGuard(dev_mode=True)
     ```
 
-    [:octicons-arrow-right-24: Python SDK](reference/sdk-python/index.md)
+    [:octicons-arrow-right-24: Agent Guard](reference/sdk-python/index.md)
 
 -   :material-shield-check:{ .lg .middle } **MCP Guard**
 

docs/reference/sdk-python/index.md

@@ -1,11 +1,11 @@
 ---
-title: Python SDK Reference
-description: Complete API reference for capiscio-sdk (auto-generated from source)
+title: Agent Guard — Python SDK Reference
+description: Complete API reference for capiscio-sdk (Agent Guard) — runtime identity and trust enforcement for A2A agents.
 ---
 
-# Python SDK Reference
+# Agent Guard — Python SDK Reference
 
-Complete API reference for the `capiscio-sdk` Python package.
+Complete API reference for the `capiscio-sdk` Python package (Agent Guard).
 
 !!! info "Auto-Generated Documentation"
     This reference is automatically generated from the SDK source code docstrings.

mkdocs.yml

@@ -239,7 +239,7 @@ nav:
           - CLI Reference: reference/cli/index.md
           - Go API: reference/go-api.md
           - gRPC Services: reference/grpc.md
-      - CapiscIO SDK:
+      - Agent Guard:
           - reference/sdk-python/index.md
           - Badge: reference/sdk-python/badge.md
           - SecurityConfig: reference/sdk-python/config.md