feat: add browser_web_search tool (real-Chrome SERP scrape, no API key)

Thin query→ranked-links primitive. Isolated-attach tab lifecycle mirroring
browser_open_urls (never touches the user's current tab); pure Google SERP
parser with semantic (a h3) extraction and redirect unwrapping; CAPTCHA and
no-results surfaced as invalid_state + details.reason. Fixture-based parser
tests (9 scenarios). Establishes the isolated-tab lifecycle and tsx+fixture
test convention that browser_read_page and deep-research build on.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

3 files changed, 48 insertions, 0 deletions

diff --git a/test/deep-research/fixtures/google-serp-captcha.json b/test/deep-research/fixtures/google-serp-captcha.json
new file mode 100644
index 0000000..7c6610f
--- /dev/null
+++ b/test/deep-research/fixtures/google-serp-captcha.json
@@ -0,0 +1,4 @@
+{
+  "anchors": [],
+  "pageText": "About this page Our systems have detected unusual traffic from your computer network. This page checks to see if it's really you sending the requests and not a robot. Why did this happen? To continue, please type the characters below. reCAPTCHA."
+}
diff --git a/test/deep-research/fixtures/google-serp-empty.json b/test/deep-research/fixtures/google-serp-empty.json
new file mode 100644
index 0000000..34bb1dc
--- /dev/null
+++ b/test/deep-research/fixtures/google-serp-empty.json
@@ -0,0 +1,4 @@
+{
+  "anchors": [],
+  "pageText": "Your search - asdkfjhqwlekjrhqwlekjrhqwe - did not match any documents. Suggestions: Make sure that all words are spelled correctly. Try different keywords."
+}
diff --git a/test/deep-research/fixtures/google-serp-ok.json b/test/deep-research/fixtures/google-serp-ok.json
new file mode 100644
index 0000000..61aa483
--- /dev/null
+++ b/test/deep-research/fixtures/google-serp-ok.json
@@ -0,0 +1,40 @@
+{
+  "anchors": [
+    {
+      "href": "https://www.google.com/url?q=https://real.example/x&sa=U&ved=abc",
+      "heading": "Real Example X — the definitive guide",
+      "snippet": "Real Example X — the definitive guide. Everything about x, explained clearly."
+    },
+    {
+      "href": "https://docs.example.org/guide",
+      "heading": "Official Guide",
+      "snippet": "Official Guide to the thing you searched for."
+    },
+    {
+      "href": "https://www.google.com/search?q=related",
+      "heading": "Related searches on Google",
+      "snippet": "internal google navigation"
+    },
+    {
+      "href": "javascript:void(0)",
+      "heading": "Expand",
+      "snippet": "ui control"
+    },
+    {
+      "href": "https://real.example/x/",
+      "heading": "Real Example X (duplicate with trailing slash)",
+      "snippet": "should be deduped against the first result"
+    },
+    {
+      "href": "https://second.example/a",
+      "heading": "Second Example A",
+      "snippet": "Second result body."
+    },
+    {
+      "href": "https://third.example/b",
+      "heading": "Third Example B",
+      "snippet": "Third result body."
+    }
+  ],
+  "pageText": "Real Example X the definitive guide Official Guide Second Example Third Example About 12,300 results"
+}