refactor settings and workspace sync modules

[LIU9293]

Summary

• centralize agent provider and provider-model selection rules in shared modules, then reuse them across Slack/Discord settings and config typing
• split workspace discover/sync logic into platform-specific modules (slack, discord, lark) with a small shared helper, and keep local-settings.ts as a facade
• extract Zod config schemas/types from packages/config/local/ode.ts into packages/config/local/ode-schema.ts while preserving existing config exports

Validation

• bun test packages/core/test/web-routes.test.ts packages/ims/slack/message-router.test.ts packages/ims/discord/api.test.ts
• bun test packages/ims/slack/message-router.test.ts packages/ims/discord/api.test.ts packages/ims/shared/incoming-pipeline.test.ts packages/ims/shared/command-router.test.ts
• bun run typecheck (still fails on pre-existing missing web-ui deps/modules: svelte components, clsx, tailwind-merge, @tailwindcss/vite)