refactor(chat,langgraph): polish Phase-1 review nits

- Drop unused ref inputs on DebugControlsComponent and DebugSummaryComponent
- Consolidate fragmented @cacheplane/chat imports in chat-debug
- Route cockpit messages/input demos through chatAgent.submit

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: blove

cockpit/chat/input/angular/src/app/input.component.ts

@@ -62,6 +62,6 @@ export class InputComponent {
   protected readonly isLoading = computed(() => this.stream.isLoading());
 
   submitMessage(content: string) {
-    this.stream.submit([{ role: 'human', content }]);
+    this.chatAgent.submit({ message: content });
   }
 }

cockpit/chat/messages/angular/src/app/messages.component.ts

@@ -54,6 +54,6 @@ export class MessagesComponent {
   protected readonly chatAgent = toChatAgent(this.stream);
 
   submitMessage(content: string) {
-    this.stream.submit([{ role: 'human', content }]);
+    this.chatAgent.submit({ message: content });
   }
 }

libs/langgraph/src/lib/compositions/chat-debug/chat-debug.component.ts

@@ -14,20 +14,23 @@ import {
 import { DomSanitizer } from '@angular/platform-browser';
 import type { AgentRef } from '../../agent.types';
 import { toChatAgent } from '../../to-chat-agent';
-import { ChatMessagesComponent } from '@cacheplane/chat';
-import { MessageTemplateDirective } from '@cacheplane/chat';
-import { ChatInputComponent } from '@cacheplane/chat';
-import { ChatTypingIndicatorComponent } from '@cacheplane/chat';
-import { ChatErrorComponent } from '@cacheplane/chat';
+import {
+  ChatMessagesComponent,
+  MessageTemplateDirective,
+  ChatInputComponent,
+  ChatTypingIndicatorComponent,
+  ChatErrorComponent,
+  messageContent,
+  CHAT_THEME_STYLES,
+  CHAT_MARKDOWN_STYLES,
+  renderMarkdown,
+} from '@cacheplane/chat';
 import { DebugTimelineComponent } from './debug-timeline.component';
 import { DebugDetailComponent } from './debug-detail.component';
 import { DebugControlsComponent } from './debug-controls.component';
 import { DebugSummaryComponent } from './debug-summary.component';
 import type { DebugCheckpoint } from './debug-checkpoint-card.component';
 import { toDebugCheckpoint, extractStateValues } from './debug-utils';
-import { messageContent } from '@cacheplane/chat';
-import { CHAT_THEME_STYLES } from '@cacheplane/chat';
-import { CHAT_MARKDOWN_STYLES, renderMarkdown } from '@cacheplane/chat';
 
 @Component({
   selector: 'chat-debug',
@@ -149,13 +152,12 @@ import { CHAT_MARKDOWN_STYLES, renderMarkdown } from '@cacheplane/chat';
 
           <!-- Summary -->
           <div class="px-3 py-2 border-b" style="border-color: var(--chat-border-light);">
-            <chat-debug-summary [ref]="ref()" [checkpoints]="checkpoints()" />
+            <chat-debug-summary [checkpoints]="checkpoints()" />
           </div>
 
           <!-- Controls -->
           <div class="px-3 py-2 border-b" style="border-color: var(--chat-border-light);">
             <chat-debug-controls
-              [ref]="ref()"
               [checkpointCount]="checkpoints().length"
               [selectedIndex]="selectedCheckpointIndex()"
               (stepForward)="stepForward()"

libs/langgraph/src/lib/compositions/chat-debug/debug-controls.component.ts

@@ -5,7 +5,6 @@ import {
   output,
   ChangeDetectionStrategy,
 } from '@angular/core';
-import type { AgentRef } from '../../agent.types';
 
 @Component({
   selector: 'chat-debug-controls',
@@ -41,7 +40,6 @@ import type { AgentRef } from '../../agent.types';
   `,
 })
 export class DebugControlsComponent {
-  readonly ref = input.required<AgentRef<any, any>>();
   readonly checkpointCount = input<number>(0);
   readonly selectedIndex = input<number>(-1);
   readonly stepForward = output<void>();

libs/langgraph/src/lib/compositions/chat-debug/debug-summary.component.ts

@@ -5,7 +5,6 @@ import {
   input,
   ChangeDetectionStrategy,
 } from '@angular/core';
-import type { AgentRef } from '../../agent.types';
 import type { DebugCheckpoint } from './debug-checkpoint-card.component';
 
 @Component({
@@ -20,7 +19,6 @@ import type { DebugCheckpoint } from './debug-checkpoint-card.component';
   `,
 })
 export class DebugSummaryComponent {
-  readonly ref = input.required<AgentRef<any, any>>();
   readonly checkpoints = input<DebugCheckpoint[]>([]);
 
   readonly totalDuration = computed(() =>