v0.13: add Quarto/xelatex PDF engine and fix ReportLab wide-table rendering

build_report.py:
- add --engine quarto option: Quarto 1.9 + xelatex pipeline with
  CJK font setup (Source Han Serif/Sans CN via fontspec),
  automatic {.landscape} wrapping for wide tables (>=8 cols),
  TOC/references placeholder replacement, sources.jsonl backfill
- prepare_qmd(): converts Markdown to .qmd with proper YAML front matter,
  writes _preamble.tex for longtable/pdflscape/lscape packages
- _detect_wide_tables(), _build_references_block(): helper functions
- ReportLab path unchanged (remains default)

report-template.py:
- render_table(): force equal-width column distribution for tables
  with >=4 cols or any cell >30 chars, preventing negative availWidth
  crash on mixed CJK/English content
- render_table_blocks(): split long tables (>25 rows) into chunks to
  avoid NoneType comparison crash in ReportLab splitByRow logic

.gitignore:
- add rules for LaTeX temp files (*.aux, xetest.*, *.qmd, _preamble.tex)
- add projects/ to gitignore (research data, not source code)

README.md:
- update status to v0.13
- rewrite PDF section as dual-engine guide with install steps,
  comparison table, and landscape table chunking guidance
- add Quarto troubleshooting (font italic mapping, tlmgr path, param_size)
- add v0.13 to changelog

.gitignore

@@ -51,3 +51,19 @@ Thumbs.db
 # ============ 归档（不纳入版本控制）============
 archive/*
 !archive/.gitkeep
+
+# ============ 临时 LaTeX / TeX 测试文件 ============
+xetest.*
+*.aux
+*.fls
+*.fdb_latexmk
+*.synctex.gz
+
+# ============ Quarto 生成的中间文件 ============
+*_files/
+*.qmd
+_preamble.tex
+
+# ============ 研究项目（实际数据，不纳入版本控制）============
+# 如需备份，请用独立的私有仓库
+projects/