Reverts the intentional broken fragment test. Workflow confirmed that
lychee does not validate heading anchors on local file URLs — it checks
file/directory existence but doesn't open index.html to verify fragments.
The ^file://.*# exclusion must remain to prevent false positives from
Hugo pretty URL resolution (lychee resolves /page#frag as file:///page
instead of file:///page/index.html).
Updated config comments to document this known gap clearly.
4d73615497