feat: Add @codebot help command for instant discoverability

Implements help command that shows all available bot commands with examples and categories.

Users can now type '@codebot help' to see complete command list without reading docs.

tests/test_ai_review.py

@@ -263,6 +263,84 @@ class TestMetrics:
         assert summary["requests"]["success"] == 1
 
 
+class TestHelpCommand:
+    """Test help command functionality."""
+
+    def test_help_command_returns_text(self):
+        """Test that help command returns formatted help text."""
+        from agents.issue_agent import IssueAgent
+
+        agent = IssueAgent(
+            gitea_client=None,
+            llm_client=None,
+            config={
+                "interaction": {
+                    "mention_prefix": "@codebot",
+                    "commands": ["help", "triage", "explain"],
+                }
+            },
+        )
+
+        help_text = agent._command_help()
+
+        assert help_text is not None
+        assert len(help_text) > 100
+        assert "@codebot" in help_text
+        assert "help" in help_text.lower()
+        assert "triage" in help_text.lower()
+
+    def test_help_includes_all_sections(self):
+        """Test that help text includes all major sections."""
+        from agents.issue_agent import IssueAgent
+
+        agent = IssueAgent(
+            gitea_client=None,
+            llm_client=None,
+            config={"interaction": {"mention_prefix": "@codebot"}},
+        )
+
+        help_text = agent._command_help()
+
+        # Check for main sections
+        assert "Issue Triage" in help_text
+        assert "Interactive Chat" in help_text
+        assert "Setup & Utility" in help_text
+        assert "Pull Request" in help_text
+        assert "Quick Examples" in help_text
+
+    def test_help_uses_custom_bot_name(self):
+        """Test that help command uses custom bot name from config."""
+        from agents.issue_agent import IssueAgent
+
+        agent = IssueAgent(
+            gitea_client=None,
+            llm_client=None,
+            config={"interaction": {"mention_prefix": "@mybot"}},
+        )
+
+        help_text = agent._command_help()
+
+        assert "@mybot" in help_text
+        assert "@codebot" not in help_text
+
+    def test_help_includes_examples(self):
+        """Test that help text includes usage examples."""
+        from agents.issue_agent import IssueAgent
+
+        agent = IssueAgent(
+            gitea_client=None,
+            llm_client=None,
+            config={"interaction": {"mention_prefix": "@codebot"}},
+        )
+
+        help_text = agent._command_help()
+
+        # Check for example commands
+        assert "triage" in help_text
+        assert "explain" in help_text
+        assert "setup-labels" in help_text
+
+
 class TestLabelSetup:
     """Test label setup and schema detection."""