Add comprehensive agent documentation

- Created hub/agents/overview.mdx with detailed agent concepts, usage patterns, and pre-configured agent listings
- Created hub/agents/create-and-edit.mdx with step-by-step guides for building custom agents
- Updated hub/agents/intro.mdx to be a focused getting-started guide with quick start flow
- Added agent pages to docs.json navigation structure
- Aligned documentation with Mission Control UI and actual agent capabilities
- Included references to cookbook agents and MCP integration examples

Generated with [Continue](https://continue.dev)

Co-Authored-By: Continue <[email protected]>

Author: BekahHW

docs/docs.json

@@ -56,8 +56,12 @@
               },
               {
                 "group": "Agents",
-                "icon": "cloud",
-                "pages": ["hub/agents/intro"]
+                "icon": "robot",
+                "pages": [
+                  "hub/agents/intro",
+                  "hub/agents/overview",
+                  "hub/agents/create-and-edit"
+                ]
               },
               "hub/sharing",
               "hub/source-control"