feat(hooks): allow message_submit to transform submitted text

web/app/[locale]/docs/page.tsx

@@ -184,6 +184,11 @@ command = "~/.codewhale/hooks/pre.sh"        # / message_submit / mode_change /
                 <p className="mt-4 text-sm text-ink-soft">
                   完整参考：<Link className="body-link" href="https://github.com/Hmbown/CodeWhale/blob/main/config.example.toml">config.example.toml</Link>。
                 </p>
+                <p className="mt-3 text-sm text-ink-soft leading-[1.9]">
+                  <code className="inline">message_submit</code> hooks run before a user message is sent to the model. A non-background hook can print
+                  <code className="inline">{'{"text":"replacement"}'}</code> on stdout to replace the message, or exit with code <code className="inline">2</code> to block the submission.
+                  <code className="inline">shell_env</code> keeps its existing <code className="inline">KEY=VALUE</code> stdout contract.
+                </p>
               </section>
 
               {/* MCP */}
@@ -434,6 +439,11 @@ command = "~/.codewhale/hooks/pre.sh"        # / message_submit / mode_change /
                 <p className="mt-4 text-sm text-ink-soft">
                   Full reference: <Link className="body-link" href="https://github.com/Hmbown/CodeWhale/blob/main/config.example.toml">config.example.toml</Link>.
                 </p>
+                <p className="mt-3 text-sm text-ink-soft leading-relaxed">
+                  <code className="inline">message_submit</code> hooks run before a user message is sent to the model. A non-background hook can print
+                  <code className="inline">{'{"text":"replacement"}'}</code> on stdout to replace the message, or exit with code <code className="inline">2</code> to block the submission.
+                  <code className="inline">shell_env</code> keeps its existing <code className="inline">KEY=VALUE</code> stdout contract.
+                </p>
               </section>
 
               <section id="mcp" className="scroll-mt-32">
@@ -547,4 +557,4 @@ command = "~/.codewhale/hooks/pre.sh"        # / message_submit / mode_change /
       )}
     </>
   );
-}
+}