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/acp-client-fs.ts

@@ -0,0 +1,35 @@
+import { promises as fs } from 'node:fs';
+import { dirname, isAbsolute, join, resolve } from 'node:path';
+
+/** Resolve an ACP path against the agent worktree and read a slice of lines. */
+export async function readWorktreeTextFile(
+  worktreePath: string,
+  filePath: string,
+  line?: number | null,
+  limit?: number | null,
+): Promise<string> {
+  const absolute = isAbsolute(filePath) ? filePath : resolve(worktreePath, filePath);
+  if (!absolute.startsWith(resolve(worktreePath))) {
+    throw new Error(`path escapes worktree: ${filePath}`);
+  }
+  const raw = await fs.readFile(absolute, 'utf8');
+  if (!line && !limit) return raw;
+  const lines = raw.split(/\r?\n/);
+  const start = Math.max((line ?? 1) - 1, 0);
+  const end = limit ? start + limit : undefined;
+  return lines.slice(start, end).join('\n');
+}
+
+/** Write a file inside the worktree (creates parent dirs). */
+export async function writeWorktreeTextFile(
+  worktreePath: string,
+  filePath: string,
+  content: string,
+): Promise<void> {
+  const absolute = isAbsolute(filePath) ? filePath : resolve(worktreePath, filePath);
+  if (!absolute.startsWith(resolve(worktreePath))) {
+    throw new Error(`path escapes worktree: ${filePath}`);
+  }
+  await fs.mkdir(dirname(absolute), { recursive: true });
+  await fs.writeFile(absolute, content, 'utf8');
+}