test(mcp): suppress webbrowser.open during browser-test fixture

`fastmcp dev apps` (spawned by the browser-test fixture) unconditionally
calls `webbrowser.open(dev_url)` at startup with no flag to disable.
Set BROWSER=true in the subprocess env so Python's webbrowser module
dispatches to the `true` command (resolved via PATH — exits 0, opens
nothing) instead of macOS's AppleScript browser-opener. Playwright
continues to drive headless Chromium for the actual render tests;
only the spurious developer-facing window is gone.

The override is skipped on Windows — there's no `true` command there,
and webbrowser would fall through to the default browser. The suite
is documented as macOS/Linux-only anyway, matching the
`start_new_session` guard a few lines below.

uv.lock is the workspace-version bump from `client v0.62.0` on main,
bundled per CLAUDE.md to keep the lockfile in sync with pyproject.toml.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dougborg

katana_mcp_server/tests/browser/conftest.py

@@ -93,7 +93,18 @@ def apps_dev_server() -> Iterator[str]:
             str(_DEV_PORT),
             "--no-reload",
         ],
-        env={**os.environ, "FASTMCP_LOG_LEVEL": "WARNING"},
+        # ``fastmcp dev apps`` unconditionally calls ``webbrowser.open(dev_url)``
+        # on startup with no flag to disable it. Setting ``BROWSER=true`` makes
+        # Python's webbrowser module dispatch to the ``true`` command (resolved
+        # via PATH) — exits 0, opens nothing. Skipped on Windows: there's no
+        # ``true`` there, and webbrowser would fall through to the default
+        # browser. The suite is documented as macOS/Linux-only, matching the
+        # ``start_new_session`` guard below.
+        env={
+            **os.environ,
+            "FASTMCP_LOG_LEVEL": "WARNING",
+            **({"BROWSER": "true"} if sys.platform != "win32" else {}),
+        },
         stdout=subprocess.DEVNULL,
         stderr=subprocess.DEVNULL,
         start_new_session=sys.platform != "win32",