docs: refresh OpenClaw integration and gateway docs

[typelicious]

What changed

• refreshed the OpenClaw integration files so provider ids, image routing, and local/image provider examples match current FoundryGate behavior
• updated the FoundryGate skill and the integration/configuration/onboarding/troubleshooting docs to explain OpenClaw model-id mapping, image routing, and the current operator surfaces
• added a direct OpenClaw integration link from the root README

Why

The OpenClaw examples and surrounding docs had drifted behind the current FoundryGate runtime. This aligns the repo with the current provider-id model, image routing support, and client-profile behavior.

How verified

• searched the repo for lingering ClawGate references in the touched areas
• git diff --check
• reviewed the updated examples against the current /v1/models, /api/route, and /api/route/image behavior