feat(steering): add AfterModelCallEvent steering documentation (strands-agents#451)

Author: dbschmigelski

docs/user-guide/concepts/experimental/steering.md

@@ -29,24 +29,48 @@ flowchart LR
 
 ## Steering
 
-When agents attempt tool calls, steering handlers evaluate the action and provide guidance:
+Steering handlers can intercept agent behavior at two points: before tool calls and after model responses.
+
+### Tool Steering
+
+When agents attempt tool calls, steering handlers evaluate the action via `steer_before_tool()`:
 
 ```mermaid
 flowchart LR
     A[Tool Call Attempt] --> B[BeforeToolCallEvent]
-    B --> C["Handler.steer()"]
-    C --> D{SteeringAction}
+    B --> C["Handler.steer_before_tool()"]
+    C --> D{ToolSteeringAction}
     D -->|Proceed| E[Tool Executes]
     D -->|Guide| F[Cancel + Feedback]
     D -->|Interrupt| G[Human Input]
 ```
 
-**SteeringHandler** intercepts tool calls via BeforeToolCallEvent, evaluates using local `steering_context`, and returns a **SteeringAction**:
+**Tool steering** returns a `ToolSteeringAction`:
 
 - **Proceed**: Tool executes immediately
 - **Guide**: Tool cancelled, agent receives contextual feedback
 - **Interrupt**: Tool execution paused for human input
 
+### Model Steering
+
+After each model response, steering handlers can evaluate output via `steer_after_model()`:
+
+```mermaid
+flowchart LR
+    A[Model Response] --> B[AfterModelCallEvent]
+    B --> C["Handler.steer_after_model()"]
+    C --> D{ModelSteeringAction}
+    D -->|Proceed| E[Response Accepted]
+    D -->|Guide| F[Discard + Retry]
+```
+
+**Model steering** returns a `ModelSteeringAction`:
+
+- **Proceed**: Accept the response as-is
+- **Guide**: Discard the response and retry with guidance injected into the conversation
+
+This enables handlers to validate model responses, ensure required tools are used before completion, or guide conversation flow based on output.
+
 ## Getting Started
 
 ### Natural Language Steering
@@ -95,7 +119,7 @@ sequenceDiagram
     participant A as Agent
     participant S as Steering Handler
     participant T as Tool
-    
+
     U->>A: "Send frustrated email to client"
     A->>A: Reason about request
     A->>S: Evaluate send_email tool call
@@ -106,8 +130,6 @@ sequenceDiagram
 
 
 
-
-
 ## Built-in Context Providers
 
 ### Ledger Provider