fix: align runtime host check with OpenClaw >=2026.5.12

[DSeaStar]

Summary

• package.json already requires OpenClaw >=2026.5.12 (peerDependencies.openclaw and openclaw.install.minHostVersion). Changelog 2.4.5 records that bump from >=2026.3.22.
• The runtime guard (SUPPORTED_HOST_MIN in src/compat.ts) and both READMEs were still advertising >=2026.3.22.
• Hosts on 2026.3.22–2026.5.11 could therefore load the plugin and then fail on the newer ctx.channelRuntime contract, instead of getting the intended clear version error.

This syncs the fail-fast check, tests, and EN/ZH docs with the published requirement. Official channel docs already describe 2.x as >=2026.5.12: https://docs.openclaw.ai/channels/wechat

Test plan

• SUPPORTED_HOST_MIN matches package.json (>=2026.5.12)
• Compat tests updated for the new floor (accept 2026.5.12 / 2026.5.13, reject 2026.5.11)
• npx vitest run src/compat.test.ts on the PR CI
• Confirm troubleshooting heading matches the error string thrown by assertHostCompatibility

[NewFuture]

Thanks for aligning the official package metadata and runtime guard. The community-maintained distribution addressed the same consistency problem independently in community PR #33, released in v3.0.1 (the current npm release is v3.1.6).

The community package deliberately maintains the stricter OpenClaw >=2026.6.1 boundary: its runtime guard, peer dependency, install metadata, documentation, and real-host compatibility matrix all use that same minimum. We therefore did not port the lower 2026.5.12 baseline, but the conflicting minimum-version declarations are not present in the community release.

This is a community release status update, not a claim that this Tencent PR has been merged upstream:
NewFuture/openclaw-weixin#33
https://www.npmjs.com/package/openclaw-weixin