fix(reply): make block streaming configurable

[wowyuarm]

Summary

• add blockStreaming to the Weixin channel/account config schema
• stop hard-coding disableBlockStreaming: true in reply dispatch
• keep existing behavior by default: block streaming stays off unless configured
• publish channelConfigs.openclaw-weixin in openclaw.plugin.json so the host sees the channel config before runtime loads
• add tests for schema parsing and account-level override behavior

Testing

• npm run typecheck
• npm run build
• npx vitest run src/messaging/process-message.test.ts src/config/config-schema.test.ts src/api/config-cache.test.ts

Full npm test still has the existing unrelated failure on main:

• src/auth/pairing.test.ts > registerUserInFrameworkStore > uses withFileLock for concurrency safety
• expected "spy" to be called 1 times, but got 0 times