Batch Generate And Save

Batch generate intents + page summaries and auto-save for multiple captures.

For each capture:

1. Generate intent mappings via vision LLM
2. Generate page summary for main agent handoff
3. Bulk save (element labels, intents, vocabulary, product route)
4. Mark capture as "processed"

Streams progress as newline-delimited JSON (NDJSON) so the UI can show live updates.

Skips captures that already have "processed" status unless force=True.