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/coder/src/services/agent-turn-persist.ts

@@ -0,0 +1,56 @@
+import type { Sql } from '../db.js';
+import type { AcpToolSnapshot } from './acp-tool-snapshot.js';
+import { snapshotToPartPayload } from './acp-tool-snapshot.js';
+
+interface PartInsert {
+  message_id: string;
+  sequence: number;
+  kind: 'reasoning' | 'tool_call';
+  payload: unknown;
+}
+
+async function insertParts(sql: Sql, parts: PartInsert[]): Promise<void> {
+  if (parts.length === 0) return;
+  await sql`
+    INSERT INTO message_parts ${sql(
+      parts.map((p) => ({
+        message_id: p.message_id,
+        sequence: p.sequence,
+        kind: p.kind,
+        payload: sql.json(p.payload as never),
+      })),
+      'message_id',
+      'sequence',
+      'kind',
+      'payload',
+    )}
+  `;
+}
+
+/** Persist external-agent reasoning + tool calls into message_parts for reload. */
+export async function persistExternalAgentTurn(
+  sql: Sql,
+  assistantMessageId: string,
+  snapshots: AcpToolSnapshot[],
+  reasoningText: string,
+): Promise<void> {
+  const parts: PartInsert[] = [];
+  let seq = 0;
+  if (reasoningText.trim()) {
+    parts.push({
+      message_id: assistantMessageId,
+      sequence: seq++,
+      kind: 'reasoning',
+      payload: { text: reasoningText },
+    });
+  }
+  for (const snapshot of snapshots) {
+    parts.push({
+      message_id: assistantMessageId,
+      sequence: seq++,
+      kind: 'tool_call',
+      payload: snapshotToPartPayload(snapshot),
+    });
+  }
+  await insertParts(sql, parts);
+}