feat(baoyu-post-to-wechat): add remote-api publishing via SSH SOCKS5 tunnel

Re-implements PR #156 (remote WeChat API publishing for IP-allowlist
constraints) with a fully local code path: spawn a background `ssh -N -D`
SOCKS5 dynamic forward, wrap a `SocksProxyAgent`, and thread it through
the existing token/upload/draft flow. No Python helper, no SCP, no
remote files, no `AppSecret` ever leaving the local process.

Reusing `uploadImagesInHtml` (which replaces the matched `<img>` fullTag
rather than substring-replacing `src`) naturally avoids the original
PR's `html.replace(src, url)` HTML-replacement bug.

Changes:
- New `wechat-remote-publish.ts`: typed-whitelist SSH args, free-port
  allocation, SOCKS readiness polling, signal-handler-backed cleanup.
- New `wechat-http.ts`: minimal `https.request`-backed HTTP helper so a
  `SocksProxyAgent` can be passed through (undici `fetch` ignores agent).
- New `wechat-image-loader.ts`: extracts `loadUploadAsset` for reuse.
- `wechat-api.ts`: thread optional `agent?` through token/upload/draft;
  add `--remote*` CLI flags; dispatch via `withSshTunnel` when remote
  mode is selected by flag or `default_publish_method: remote-api`.
- `wechat-extend-config.ts`: add typed `remote_publish_*` keys with
  account-over-global fallback and value validation.
- Docs: SKILL.md, references/multi-account.md, references/config/
  first-time-setup.md, README.md, README.zh.md.
- Tests: 17 new node:test cases covering config parsing, SSH arg
  whitelisting, free-port allocation, multipart assembly, and HTTP
  agent threading.

Co-authored-by: Dame5211 <1079825614@qq.com>

skills/baoyu-post-to-wechat/scripts/package.json

@@ -6,6 +6,7 @@
     "@jsquash/webp": "^1.5.0",
     "baoyu-chrome-cdp": "^0.1.0",
     "baoyu-md": "^0.1.0",
-    "jimp": "^1.6.0"
+    "jimp": "^1.6.0",
+    "socks-proxy-agent": "^10.0.0"
   }
 }