Add a new command that configures popular coding agents (Claude Code,
Qwen Code, OpenCode, OpenClaw, Hermes, Codex) to use DashScope API
with a single copy-paste command from the web console.

Supports Linux, macOS, and Windows. Non-destructively merges into
existing config files with automatic backup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- OpenCode/OpenClaw/Hermes: dynamically choose API protocol based on
  whether the base-url is an anthropic endpoint or openai-compatible
- Codex: write ~/.codex/auth.json alongside config.toml so users
  don't need to manually export OPENAI_API_KEY
- Add shared isAnthropicEndpoint() helper in writers/utils.ts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Two variants:
- via-bailian-cli/: uses npx bailian-cli (requires Node.js 22+)
- pure/: zero dependencies, writes config files directly in bash/PowerShell

Supports all 6 agents with API protocol auto-detection from base-url.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

… files

Move agent configuration command under the `config` command group for
better semantic alignment. Relocate all related files from
`commands/agent/` into `commands/config/agent/`.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>