Revert #82 (Modern Web Guidance rung-3) and re-sync mirrors (#178)

#82 added a "Web tasks: rung 3 lookup" section to the always-on ponytail
SKILL.md, about an external `modern-web` CLI most users won't have installed.
It's optional bloat in the always-on ruleset, and it broke CI by leaving the
.openclaw mirror stale.

Reverts the section from skills/ponytail/SKILL.md, the README callout, and
examples/web-platform-lookup.md, then regenerates the .openclaw mirror and
removes the Spanish callout that #174 had mirrored. Suite green (56/56).

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>