[Feature]: Commands that are misspelled in the message channel are still forwarded to the agent

## QwenPaw Version

2.0.0-beta.5

## Description

When I send incorrect commands to the QQ(or others) channel, the agent can still receive these commands and process them as messages instead of discard these erroneous commands and inform the user.

For example, spelling `/new` as `/mew`. At this point, the model will unexpectedly start working.

In addition, the `/help` command is not currently supported, which makes it difficult for users to remember which commands are available when they forget them, and the specific command format.

## Component(s) Affected

- [x] Core / Backend (app, agents, config, providers, utils, local_models)
- [ ] Console (frontend web UI)
- [x] Channels (DingTalk, Feishu, QQ, Discord, iMessage, etc.)
- [ ] Skills
- [ ] CLI
- [ ] Documentation (website)
- [ ] Tests
- [ ] CI/CD
- [ ] Scripts / Deploy

## Actual vs Expected

- **Actual:** These erroneous commands will be passed directly to Agent.
- **Expected:**
1. The command should be rejected, and the user should be told that the command is incorrect and that they should enter the `/help` command to view relevant help.
2. If the user is using a skill, which skill name should be provided that is closest to the corresponding skill

Trace command dispatch for the QQ and other message channels in the Core / Backend and Channels components, starting with how `/new` is recognized and forwarded. Check the existing command responses and skill-name handling; done means unknown commands are rejected with guidance to use `/help`, `/help` lists the available format, and applicable skill names can be suggested.

Vom Indexierungsmodell aus dem Issue-Text verfasst.