Plugin: avoid vendored OpenClaw fallbacks

[huntharo]

Summary

I fixed the packaged-install Discord compatibility path that was still resolving runtime fallbacks from the extension's own vendored node_modules/openclaw copy instead of the host OpenClaw runtime.

• I moved openclaw out of peerDependencies and into devDependencies so the plugin no longer advertises OpenClaw as something to install alongside the extension at runtime.
• I hardened the compat resolver to prefer the real host OpenClaw process location, including a require.main fallback for packaged installs.
• I explicitly reject extension-local OpenClaw roots under ~/.openclaw/extensions/... so Discord fallback imports cannot accidentally bind to a vendored package tree.
• I added regression tests for the require.main host fallback and for rejecting extension-local vendored openclaw copies.

Testing

• bun node_modules/vitest/vitest.mjs run -- src/openclaw-sdk-compat.test.ts src/controller.test.ts
• bun node_modules/typescript/bin/tsc --noEmit