fix(ci): use an explicit browser demo dependency (#4185)

The security-update checker on main expects dependency-group entries to
be requirement strings and crashes on the browser-demo group's
include-group entry, blocking #4127.

Replace that alias with `playwright==1.63.0`, the exact requirement
already declared by provider-browser. The final change is one line in
pyproject.toml. Package versions, the resolved dependency graph, and
uv.lock remain unchanged.

Validation: Python policy check, focused dependency-policy tests, and
CI. This must land on main first because #4127's security gate executes
the checker from the immutable base commit.

Author: marcuswood-oai

pyproject.toml

@@ -73,7 +73,7 @@ pydantic-v1 = ["pydantic>=1.10.26,<2"]
 pydantic-v2 = ["pydantic>=2,<3"]
 provider-computer = ["Pillow==12.3.0"]
 provider-browser = ["playwright==1.63.0"]
-browser-demo = [{ include-group = "provider-browser" }]
+browser-demo = ["playwright==1.63.0"]
 # Isolated build requirements are exported with hashes by scripts/build.
 build = [
     "hatchling==1.32.4",