fix(extension): roll back CDP attach when a domain enable fails

[hobostay]

Problem

ChromiumCdp.ensureAttached can leave a tab permanently stuck when a CDP domain enable fails after the raw attach succeeds.

The attach sequence was:

await this.api.attach({ tabId }, CDP_PROTOCOL_VERSION); // succeeds -> Chrome has the debugger attached
await this.enablePageDomain(tabId);                     // can throw (Page.enable)
await this.enableConsoleDomains(tabId);                 // best-effort (swallows)
await this.enableNetworkDomainBestEffort(tabId);        // best-effort (swallows)
this.attachedTabs.add(tabId);                           // only reached if all of the above succeed

enablePageDomain is the only domain enable that is neither best-effort nor guarded. If it rejects — e.g. the tab navigates to a chrome:// URL or the Web Store in the gap between attach and Page.enable, or a transient CDP error during attach — the .catch re-throws but performs no cleanup, and attachedTabs never records the tabId.

On the next tool call, ensureAttached sees the tabId is not cached, has no in-flight attach, and calls api.attach again → Chrome rejects it with "Another debugger is already attached". Every subsequent operation on that tab fails until the extension is reloaded. Note the public detach() cannot self-heal this, because it no-ops when attachedTabs lacks the id.

Fix

Detach the debuggee directly in the failure path (before re-throwing) so the next attempt starts from a clean slate:

await this.api.attach({ tabId }, CDP_PROTOCOL_VERSION);
try {
  await this.enablePageDomain(tabId);
  await this.enableConsoleDomains(tabId);
  await this.enableNetworkDomainBestEffort(tabId);
  this.attachedTabs.add(tabId);
} catch (err) {
  await this.api.detach({ tabId }).catch((detachErr) => {
    console.debug("[bsk cdp] rollback detach failed", { tabId, detachErr });
  });
  throw err;
}

api.attach failures are untouched (no detach attempted, since nothing was attached) — only failures after a successful attach roll back.

Test

Adds a regression test that mocks Page.enable to throw after attach succeeds, then asserts:

• ensureAttached rejects with the original error,
• the rollback calls api.detach({ tabId }),
• the tab is not left in the cache, and
• a fresh ensureAttached succeeds afterwards.

This test fails on the previous code (0 detach calls) and passes with the fix.

Validation

Ran the frontend CI gates locally against this branch:

• pnpm --filter @browser-skill/extension exec wxt prepare ✅
• pnpm ext:test — 388 passed ✅
• pnpm --filter @browser-skill/extension compile (tsc --noEmit) ✅
• pnpm lint (biome + stylelint) ✅
• pnpm ext:build ✅

🤖 Generated with Claude Code