Update docs

Author: mitsuhiko

packages/coding-agent/docs/extensions.md

@@ -535,12 +535,12 @@ pi.on("tool_call", async (event, ctx) => {
 
 #### before_bash_exec
 
-Fired before a bash command executes (tool calls and user `!`/`!!`). Use it to rewrite commands or override execution settings.
+Fired before a bash command executes (tool calls and user `!`/`!!`). Use it to rewrite commands or override execution settings. You can also block execution by returning `{ block: true, reason?: string }`. For follow-up hints based on output, pair this with `tool_result`.
 
 ```typescript
 pi.on("before_bash_exec", async (event) => {
   if (event.command.includes("rm -rf")) {
-    return { command: "echo blocked" };
+    return { block: true, reason: "Blocked by policy" };
   }
 
   if (event.source === "tool") {
@@ -560,7 +560,7 @@ Return a `BashExecOverrides` object to override fields, or return `{ block: true
 
 #### tool_result
 
-Fired after tool executes. **Can modify result.**
+Fired after tool executes. **Can modify result.** Use this to post-process outputs (for example, append hints or redact secrets) before the result is sent to the model.
 
 ```typescript
 import { isBashToolResult } from "@mariozechner/pi-coding-agent";