fix: support multiple -c collection filters in search/query/vsearch

[neomatrixyzy]

Summary

Fix for #175 — multiple -c / --collection flags are now properly supported across all search modes.

The Bug

parseArgs in qmd.ts used type: "string" without multiple: true for the collection option. When passing -c plans -c sessions, only "sessions" (the last value) was kept. This silently broke multi-collection search workflows.

The Fix

qmd.ts (CLI layer)

• Added multiple: true to parseArgs collection option
• Added normalizeCollectionFilter() helper to normalize string | string[] → string[] | undefined
• Updated search(), vectorSearch(), and querySearch() to validate and pass collection arrays

store.ts (search engine layer)

• searchFTS: collectionId?: number → collectionNames?: string[], SQL = ? → IN (?, ?, ...)
• searchVec: collectionName?: string → collectionNames?: string[], SQL = ? → IN (?, ?, ...)
• Updated CJK fallback paths (trigram + LIKE) for multi-collection support
• Updated Store interface, HybridQueryOptions, VectorSearchOptions
• Updated all internal callers in hybridQuery and vectorSearchQuery

Testing

# Before fix: only searches last collection
qmd search "Apple TV" -c plans -c sessions -n 5 --files
# → only "sessions" results (or empty)

# After fix: searches both collections
qmd search "Apple TV" -c plans -c sessions -n 5 --files
# → results from both plans AND sessions ✅

# Single -c backward compatible
qmd search "test" -c plans -n 3 --files  # ✅ works as before

# All three modes verified
qmd search  "query" -c a -c b  # ✅
qmd query   "query" -c a -c b  # ✅
qmd vsearch "query" -c a -c b  # ✅

Files Changed

• src/qmd.ts — parseArgs + command handlers (~20 lines)
• src/store.ts — search functions + interfaces (~40 lines)

Fixes #175