Slice 4: Theme Provider

[qwerkilo]

Parent

#1 — context2html Framework

What to build

Extend theme/theme-index.json with recommendation fields, then build context2html/theme.py that provides programmatic access to 20 brand themes.

theme-index.json extension — add two optional fields per theme entry:

{
  "name": "warm",
  "display_name": "暖阳",
  "brand": "default",
  "accent": "#c0392b",
  "bg": "#faf9f7",
  "recommend_for": ["report", "article"],
  "recommend_topics": ["经济", "社会", "教育"]
}

Existing entries keep working — recommend_for and recommend_topics are optional, defaulting to all content types / empty topic list.

ThemeProvider API:

• ThemeProvider.list_themes() → list of ThemeInfo (name, display_name, brand, accent, bg)
• ThemeProvider.get_theme(name) → ThemeInfo with all variables
• ThemeProvider.recommend_theme(content_type, topic=None) → theme name string
  • Exact topic match (check recommend_topics includes topic) → exact content type match → fall back to warm

Acceptance criteria

• theme/theme-index.json has the new fields for all 20 themes
• get_theme("warm") returns a ThemeInfo with accent="#c0392b", bg="#faf9f7"
• recommend_theme("report", "经济") returns a reasonable theme (not just "warm" for everything)
• recommend_theme("blog", null) — unknown content type — returns default ("warm")
• Tests use theme/theme-index.json as-is to catch schema drift
• All 376 existing tests still pass

Blocked by

• Slice 1: Python package scaffolding (prefactor) #2