feat(docs): launch landing/docs site with skill + installer publishing

[vrknetha]

Summary

• Launches the new landing/docs app at apps/landing (Astro + Starlight) with the full docs IA and landing experience.
• Publishes a single canonical skill artifact at /skill.md generated from the source skill + reference docs.
• Adds hosted installer endpoints /install.sh and /install.ps1 and aligns docs/skill guidance to the current Rust CLI flow.
• Adds Cloudflare Pages deployment workflows for develop (preview) and main (production), including project bootstrap/assertions.
• Updates Rust release automation to publish Windows ARM64 binary artifacts and ship installer scripts with releases.
• Removes stale legacy docs and aligns AGENTS/docs references across repo areas touched by the docs-site rollout.

Key Changes

• New landing/docs app files under apps/landing/** (content, components, styles, assets, scripts).
• New workflows:
  • .github/workflows/deploy-landing-develop.yml
  • .github/workflows/deploy-landing.yml
• Updated workflow:
  • .github/workflows/publish-rust.yml
• Updated skill/docs source:
  • apps/openclaw-skill/skill/SKILL.md
  • apps/openclaw-skill/skill/references/*.md

Validation

• Pre-push hook passed full Nx affected quality gates (lint/format/typecheck/test) for impacted projects.
• Landing checks/build completed in prior validation runs for this branch.

Notes

• This push force-updated feature/docs-site to the recovered branch history.
• PR base: develop.