refactor(extension): class-based command registry + modular src layout

Restructure the MV3 background worker from a monolithic core.ts/index.ts
into a class-based command architecture. Behavior is identical — the 83
registered commands dispatch byte-for-byte the same as before.

Structure
- One class per command group, each extending CommandGroup and exporting a
  `commands` map keyed by the full command id ("tabs.close"). Groups:
  Navigation, TabsMutation, TabsQuery, Groups, Windows, Dom (dom/extract/
  page), BrowserData (storage/cookies), Session (session/clients + autosave
  + lazy-tab activation), Perf (perf + jobs.status/cancel), Extension.
- CommandRegistry merges the group maps (throws on duplicate ids), routes
  background specs to JobManager and paginates array results via
  makePagedData. JobManager owns the job map + lifecycle. NativeConnection
  owns the native-port lifecycle and the inbound message router.
- index.ts is now thin wiring: JobManager -> ctx -> assembleRegistry ->
  onActivated -> NativeConnection.start().
- Infra classes live in classes/ (PascalCase, file = class name); command
  groups in commands/; shared helpers split out of core.ts into core/
  (errors, throttle, scripting, tab-helpers, group-helpers, storage); all
  types moved into types/ (json, jobs, session, tabs, messages,
  command-args) behind a barrel.

DRY cleanup
- resolveTabUrl(tabId) and assertScriptableUrl(url, action) collapse the
  tab/URL-guard boilerplate duplicated across dom.ts and browser-data.ts.
- processInBatches() centralizes the throttled, cancellable batch loop
  shared by tabs.close, group.close and tabs.merge_windows.
- captureCurrentSession() dedups the snapshot-and-signature block shared by
  session.save and the autosave path.
- DomArgs type alias replaces 21 inline ContentArgs & { tabId? } copies.
- Drop fetchTabHtml's redundant retry loop (executeScript already retries
  transient frame/tab errors), a dead tabInfo import, and two stale
  comments referencing a removed asArgs helper.

Type safety & tests
- Full noImplicitAny; no `any`/`unknown` annotations remain in src.
- JS unit-test harness using node --test + node:assert (zero new deps),
  bundled via the existing esbuild. Covers JobManager retention/lifecycle
  and the autosave listener-wiring/debounce with an in-memory chrome mock.
- The structural pytest checks track the new file homes and the centralized
  processInBatches helper.

Verification: npm run check:extension green (tsc + esbuild 84.5kb +
node --check + 18 JS tests); uv run pytest -q -> 409 passed, 105 skipped.
No version bump.

extension/src/commands/windows.ts

@@ -1,34 +1,45 @@
-// @ts-nocheck
 import { getAliases } from '../core';
-export async function windowsList() {
-  const windows = await chrome.windows.getAll({ populate: true });
-  const aliases = await getAliases();
-  return windows.map(w => ({
-    id: w.id,
-    alias: aliases[w.id] || null,
-    focused: w.focused,
-    state: w.state,
-    tabCount: (w.tabs || []).length,
-  }));
-}
+import { CommandGroup } from '../classes/CommandGroup';
+import type { CommandEntry } from '../classes/CommandGroup';
+import type { WindowsRenameArgs, WindowsCloseArgs, WindowsOpenArgs } from '../types';
 
-export async function windowsRename({ windowId, name }) {
-  const aliases = await getAliases();
-  aliases[windowId] = name;
-  await chrome.storage.local.set({ windowAliases: aliases });
-  return { windowId, name };
-}
+export class WindowsCommands extends CommandGroup {
+  readonly namespace = "windows";
+  readonly commands: Record<string, CommandEntry> = {
+    "windows.list":   () => this.windowsList(),
+    "windows.rename": (a: WindowsRenameArgs) => this.windowsRename(a),
+    "windows.close":  (a: WindowsCloseArgs) => this.windowsClose(a),
+    "windows.open":   (a: WindowsOpenArgs) => this.windowsOpen(a),
+  };
 
-export async function windowsClose({ windowId }) {
-  await chrome.windows.remove(windowId);
-  return { windowId };
-}
+  private async windowsList() {
+    const windows = await chrome.windows.getAll({ populate: true });
+    const aliases = await getAliases();
+    return windows.map(w => ({
+      id: w.id,
+      alias: aliases[w.id] || null,
+      focused: w.focused,
+      state: w.state,
+      tabCount: (w.tabs || []).length,
+    }));
+  }
 
-export async function windowsOpen({ url }) {
-  const createData = { focused: true };
-  if (url) createData.url = url;
-  const w = await chrome.windows.create(createData);
-  return { id: w.id };
-}
+  private async windowsRename({ windowId, name }: WindowsRenameArgs) {
+    const aliases = await getAliases();
+    aliases[windowId] = name;
+    await chrome.storage.local.set({ windowAliases: aliases });
+    return { windowId, name };
+  }
 
-// ── DOM / Extract ─────────────────────────────────────────────────────────────
+  private async windowsClose({ windowId }: WindowsCloseArgs) {
+    await chrome.windows.remove(windowId);
+    return { windowId };
+  }
+
+  private async windowsOpen({ url }: WindowsOpenArgs) {
+    const createData: chrome.windows.CreateData = { focused: true };
+    if (url) createData.url = url;
+    const w = await chrome.windows.create(createData);
+    return { id: w.id };
+  }
+}