feat(docs): auto-resize table column widths after document create/update

[SoIomon]

Summary

When creating or updating documents via docs +create or docs +update, table columns are rendered with equal widths regardless of content. This PR adds automatic column width calculation based on cell content, similar to how spreadsheet applications auto-fit column widths.

Changes

• New file: table_auto_width.go — Post-processing logic that:

  • Fetches all document blocks after creation/update
  • Identifies table blocks
  • Calculates optimal column widths based on content (CJK chars = 2 units, ASCII = 1 unit)
  • Calls batch_update API to apply computed widths
  • Min width: 80px, Max width: 400px, Total constraint: ~700px

• New file: table_auto_width_test.go — Unit tests for width calculation, wide character detection, and pixel width constraints

• Modified: docs_create.go — Calls autoResizeTableColumns() after successful document creation

• Modified: docs_update.go — Calls autoResizeTableColumns() after overwrite/append mode updates

Design decisions

• Non-blocking degradation: If post-processing fails, only a warning is printed — document creation is never affected
• Reuses existing patterns: Uses runtime.CallAPI consistent with doc_media_insert.go

Test plan

• go build ./... passes
• go test ./shortcuts/doc/... passes
• Manual test: create document with mixed CJK/ASCII tables and verify column widths

[SoIomon]

实现有 bug，修复后重新提交