refactor: extract config.py, add burn_only, fix title_segments and font size

- Extract all path/API config to config.py (single source of truth)
- Add run.py / burn_only.py / run.bat / burn.bat entry points
- burn_only: skip transcription/subtitle gen, fast reburn existing SRTs
- Fix title_segments: use transcript keyword time for split point
- Fix subtitle: each overlapping title shows max title_duration (not full clip)
- Fix burn_only font size: default from 90 to 60
- Delete old run_lesson1.bat/py, temp debug scripts
- Update README, ARCHITECTURE, CHANGELOG, add USAGE.md

config.py

@@ -0,0 +1,24 @@
+# -*- coding: utf-8 -*-
+"""
+统一配置 - 修改这里即可，不要改 run.py / burn_only.py / *.bat
+
+所有路径和 API 配置集中管理。
+"""
+import os
+
+# ========== 路径配置 ==========
+VIDEO = r"D:\F\yc\课程上架\福田商圈夜校\课程视频\直播回放-03月18日.mp4"
+PPT = r"D:\F\yc\课程上架\福田商圈夜校\课程视频\钢琴演奏入门第一课.pptx"
+OUTPUT = r"D:\F\NewI\opencode\daily-workspace\projects\piano-lesson-highlights\cases\lesson1\output_cli_full"
+LOG_FILE = r"D:\F\NewI\opencode\daily-workspace\temp\cli_run_log.txt"
+
+# ========== 运行参数 ==========
+MAX_TOTAL_DURATION = 600  # 精华片段总时长上限（秒）
+
+# ========== API 配置 ==========
+API_KEY = "b0359bed-09f2-49e2-a53c-32ba057412e3"
+API_HOST = "https://ark.cn-beijing.volces.com/api/coding/v3"
+
+# ========== 环境（一般不改）==========
+PYTHON = r"D:\ProgramData\anaconda3\envs\py312_cuda\python.exe"
+CLI_DIR = os.path.dirname(os.path.abspath(__file__))  # 本文件所在目录