chore: validate development against OpenClaw 2026.4.8

[xsfX20]

Summary:

• bump the local OpenClaw development baseline from 2026.3.23 to 2026.4.8
• refresh the lockfile to match the tested host version
• correct the README compatibility row from 2.0.x to 2.1.x

Verification:

• npm test
• npm run typecheck

Notes:

• this is intentionally separate from test: fix pairing mock path and restore coverage #35
• this updates the development/test baseline only; it does not change runtime plugin behavior

[xsfX20]

Closing this because the branch was created from the wrong fork base and the diff is not minimal. I will reopen from a clean upstream main base.