v2.2-paseo-providers: Paseo provider stack + v2.2.1 pane-scoped chat fixes

Ship Paseo-equivalent provider snapshot, AgentComposerBar, ACP dispatch
rewrite with streaming/persist, permission prompts, and agent commands.
Follow-up: pane-scoped chat resolution, CoderMessageList tool timeline,
WS user-delta replace, and inference orphan tool_call stripping.
Archive openspec v2-2; update CHANGELOG and CURRENT.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/web/src/lib/apply-user-delta.ts

@@ -0,0 +1,11 @@
+/** User messages are inserted atomically — never stream-append like assistant deltas. */
+export function applyMessageDelta(
+  role: 'user' | 'assistant' | 'system' | 'tool',
+  existingContent: string,
+  chunk: string,
+): string {
+  if (role === 'user') {
+    return chunk || existingContent;
+  }
+  return existingContent + chunk;
+}