fix(base): default form attachment questions to all files

[hehanlin1996]

Summary

Fixes larksuiteGH-929 feedback C6 for base +form-questions-create attachment questions. Bare attachment questions now send attachment.file_types: ["all"] so forms accept PDFs, Word documents, and other files like the UI does, while explicit attachment or attachment_config input is preserved.

Changes

• Default attachment questions to attachment.file_types: ["all"] when no attachment config is provided.
• Include the normalized request body in this shortcut's dry-run output and update the --questions flag help.
• Add unit coverage for the outgoing stub body and explicit config preservation.
• Add dry-run E2E coverage and update the base E2E coverage table.

Test Plan

• Unit tests pass: go test ./shortcuts/base -run 'TestBaseFormQuestions' -count=1
• Dry-run E2E passes: LARK_CLI_BIN=/tmp/lark-cli-feedback-fix-2026-05-17/lark-cli-base-form-attachment go test ./tests/cli_e2e/base -run TestBaseFormQuestionsCreateDryRun_AttachmentDefaultsAllFiles -count=1
• Formatting check: gofmt -l shortcuts/base/base_form_questions_create.go shortcuts/base/base_form_execute_test.go tests/cli_e2e/base/base_form_questions_dryrun_test.go produced no output
• TDD failure confirmed before production code: go test ./shortcuts/base -run 'TestBaseFormQuestionsExecuteCreate/attachment_defaults_to_all_file_types' -count=1 failed before the fix

Related Issues

• form-questions-create: attachment 默认只接收图片，缺少文件类型配置参数 larksuite/cli#929