Title

fix(download): support user-token downloads with Range fallback

Summary

Fix msg resource-download when --user-access-token is provided, and add large-file Range fallback for both message resources and Drive file downloads.

The generated Lark Go SDK currently marks MessageResource.Get as tenant-token only, so passing WithUserAccessToken(...) fails with:

tenant token type not match user access token

However, the raw OpenAPI endpoint:

GET /open-apis/im/v1/messages/:message_id/resources/:file_key

can download resources with a user access token when the resource is visible to that user.

This PR preserves the existing SDK-based tenant/app-token path by default, and uses raw HTTP only when --user-access-token is explicitly provided. It also adds HTTP Range fallback for large downloads when Feishu returns file-size-limit errors.

Changes

• Use raw HTTP for message resource downloads when a User Token is provided.
• Preserve existing SDK-based tenant/app-token behavior when no User Token is provided.
• Add shared HTTP Range download helper:
  • sends Range: bytes=start-end
  • validates Content-Range
  • writes chunks sequentially
  • removes partial output on failure
• Apply Range fallback to:
  • msg resource-download
  • file download
  • drive download
  • callers using DownloadFileWithToken
• Stream successful raw downloads directly to disk instead of loading the full file into memory.
• Update command help, README, and skill docs with User Token and large-file examples.

Tests

Added tests for:

• successful User Token message resource download
• API error propagation
• no tenant token request when User Token is explicit
• message resource Range fallback
• Drive file Range fallback

Verification

• go test ./internal/client
• go test ./cmd
• git diff --check

Manual verification from the User Token resource path:

• Downloaded a real message video resource with --user-access-token
• Output content type: video/quicktime
• Output size: 3,803,728 bytes