fix: address review issues and add processes documentation

- Fix unstable onExit callback in ProcessesTab (useCallback)
- Fix SSE follow stream race condition (subscribe before history read)
- Update inspector.mdx with new process management features
- Change observability icon to avoid conflict with processes
- Add docs/processes.mdx covering the full process management API

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/docs.json

@@ -79,7 +79,7 @@
 					},
 					{
 						"group": "System",
-						"pages": ["file-system"]
+						"pages": ["file-system", "processes"]
 					},
 					{
 						"group": "Orchestration",