refactor: attach and windowId become session methods

cdp/attach.ts and cdp/window.ts were a module each for a single
`map(await session.callBrowser(...))` one-liner that took the session as
its first argument — two files, two imports and two names for what the
session can expose itself. They are now session.attach(targetId) and
session.windowId(targetId).

session.ts also repeated `targetId ? tabs.get(targetId) : undefined`
eight times; that is now currentTab().

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/src/domains/navigate.ts b/src/domains/navigate.ts
index 17e25a6..151a742 100644
--- a/src/domains/navigate.ts
+++ b/src/domains/navigate.ts
@@ -4,7 +4,6 @@ import { type Result, err, ok } from "../util/result";
 import { defineBrowserTool, type ToolErr, type ToolOk } from "../util/tool";
 import { applyTruncation } from "../util/truncate";
 import { safeJs } from "../util/js-template";
-import { attachTo } from "../cdp/attach";
 import { ensureHarnessWindow, openHarnessTab } from "../cdp/target-factory";
 import { cdpCall, cdpCallBrowser, cdpCallOnTarget, evalJs } from "./cdp-call";
 
@@ -107,7 +106,7 @@ export const openUrlsTool = defineBrowserTool({
     const settled = await Promise.all(
       created.filter((t) => t.ok).map(async (tab): Promise<TabResult> => {
         try {
-          const attached = await attachTo(client.session(), tab.targetId);
+          const attached = await client.session().attach(tab.targetId);
           if (!attached.success) return { ...tab, ok: false, error: attached.error.message };
           const sid = attached.data;
           const enabled = await cdpCallOnTarget(client, "Page.enable", {}, sid);