feat(web): render Code Mode sub-calls as native rows nested under the run_code row

The client indexes tool/code-dispatch events into
ConversationSnapshot.codeDispatches (parent callId -> ToolResultNode-shaped
sub-calls; live mux and history replay build the identical index). ChatView
renders each run_code parent as the new code variant (description summary,
program as the expanded monospace body) with its sub-dispatches as
always-visible indented rows — every sub-row dispatches through the SAME
keyed conversation.chat.toolview hole with the same GenericToolCard
fallback, so custom registrations (bash sample) take over sub-rows exactly
as top-level rows. The details panel resolves sub-callIds to full logged
args and complete output through the native path.

Evidence: fixture turn 64 + built-bundle jsdom snapshot, real-machinery
jsdom suites (nesting, error state, details, running parent, reference
stability), and a recorded code-mode browser e2e round (keyless replay +
aria golden). Scaffold gains a toolsMode patch knob.

apps/web/tests/scaffold.ts

@@ -103,6 +103,13 @@ export interface LaunchOptions {
   replayFixture?: string
   /** Per-chunk replay pacing (ms) so the browser observes genuinely incremental SSE; replay/refresh only. */
   paceMs?: number
+  /**
+   * Tool presentation mode patched onto the shipped `tools` row (`code`
+   * collapses the wire to run_code + the SDK prompt section). Omit for the
+   * yml default. The code runtime row is always in the tree, so no extra
+   * insertion is needed.
+   */
+  toolsMode?: 'native' | 'code' | 'both'
 }
 
 /** Dispose the booted tree and remove both owned temp roots, reporting every independent cleanup failure. */
@@ -154,6 +161,7 @@ export async function launchWebScaffold(options: LaunchOptions = {}): Promise<We
     { id: 'workspace-context', disabled: true },
     { id: 'session-title-llm', disabled: true },
     { id: 'webserver', config: { host: '127.0.0.1', port: 0, distIndex: DIST_INDEX } },
+    ...options.toolsMode === undefined ? [] : [{ id: 'tools', config: { mode: options.toolsMode } }],
     ...mode === 'record' ? [] : [{ id: 'llm-deepseek', disabled: true }],
   ]