fix(export): preserve themed callouts and nested table layouts

backend/app/export/themes.py

@@ -0,0 +1,33 @@
+"""Export palettes are fixed data; arbitrary theme CSS is never executed."""
+PALETTES = {
+    'light': ('#f6f7f9','#ffffff','#1f2328','#57606a','#eaeef2','#d0d7de','#0969da'),
+    'dark': ('#010409','#0d1117','#e6edf3','#b1bac4','#21262d','#57606a','#79c0ff'),
+    'sepia': ('#eee5d2','#faf4e6','#463b2d','#6b5943','#eae0cd','#b5a58b','#80532a'),
+    'paper-moments': ('#f4ede0','#fffdf4','#514638','#79654f','#eee7d8','#b8a58f','#8c503b'),
+    'midnight-purple': ('#100c18','#191322','#eee7f8','#c0accf','#30253f','#705a85','#d3a7ff'),
+}
+
+def html_theme(theme_id, warnings):
+    if theme_id not in PALETTES:
+        warnings.append(f'HTML 不支持主题 {theme_id}，已使用 light 导出配色')
+        theme_id = 'light'
+    names = ('page','surface','text','muted','code','border','accent')
+    return theme_id, ':root{' + ';'.join(f'--{k}:{v}' for k,v in zip(names,PALETTES[theme_id])) + '}'
+
+def print_theme_warning(options, warnings, format_name):
+    if options.theme_id != 'light':
+        warnings.append(f'{format_name} 使用浅色打印样式，不支持主题 {options.theme_id}；需要主题配色请导出 HTML')
+
+# Semantic type, portable title symbol and contrasting print color.
+CALLOUTS = {
+    'note': ('i','#0969da'), 'abstract': ('=','#7041a0'),
+    'info': ('i','#0969da'), 'todo': ('[ ]','#0969da'),
+    'tip': ('+','#176f41'), 'success': ('+','#176f41'),
+    'question': ('?','#805400'), 'warning': ('!','#805400'),
+    'failure': ('x','#b42318'), 'danger': ('!','#b42318'),
+    'bug': ('!','#b42318'), 'important': ('!','#7041a0'), 'example': ('*','#7041a0'), 'quote': ('>','#57606a'),
+}
+ALIASES = {'summary':'abstract','tldr':'abstract','hint':'tip',
+           'check':'success','done':'success','help':'question','faq':'question',
+           'caution':'warning','attention':'warning','fail':'failure','missing':'failure',
+           'error':'danger','cite':'quote'}