[MEDIUM] feat: Add subject-based (thematic) search

[adelpro]

Content:

Today, semantic search in src/core/layers/semantic-search.ts only expands to a flat list of synonyms from src/data/semantic.json. Searching for "climate" returns nothing because the engine has no concept of themes — rain, wind, tornadoes are not connected.

Add a subject search mode (options.subject = true) backed by a curated subject graph: each node groups related Arabic lemmas/roots by theme (weather, emotions, family, worship, etc.).

Requirements:

• New JSON file src/data/subjects.json (ships an initial seed/template — see issue [Easy] Sura Metadata Constants #2).
  -New loader loadSubjectData() exported from src/index.ts.
• Add subjectMap?: Map<string, SubjectNode> to SearchContext.
• Add subjectIndex?: Map<string, Set> to InvertedIndex, built by buildInvertedIndex.
• New performSubjectSearch() in src/core/layers/.
• Score hits with matchType: 'subject' (also add to MatchType union and SearchCounts).
  Example:

search('climate', { /* ... */ subjectMap }, { subject: true });
// returns verses containing أمطار، رياح، عواصف، بروق، رعد، سحاب ...
Files / Links:

https://github.com/adelpro/quran-search-engine/blob/main/src/core/layers/semantic-search.ts
https://github.com/adelpro/quran-search-engine/blob/main/src/data/semantic.json
https://github.com/adelpro/quran-search-engine/blob/main/src/utils/loader.ts
https://github.com/adelpro/quran-search-engine/blob/main/src/types/index.ts
https://github.com/adelpro/quran-search-engine/blob/main/src/core/search.ts
https://github.com/adelpro/quran-search-engine/blob/main/src/index.ts
https://github.com/adelpro/quran-search-engine/blob/main/README.md

[SolomDev00]

Assign to me please.

[adelpro]

ok @SolomDev00

[adelpro]

Salam @SolomDev00

Checking in since there hasn't been an update in a while. Are you still interested in this issue? If I don't hear back, I'll unassign it so someone else can pick it up.