Extract agent, compact, embed, task, and modes modules from single
service.rs files into focused sub-modules. Add orao module for
O1-like reasoning loop. Move RigAgentService to rig_tool.rs.
- chunk_text(): char-boundary-safe text chunking at paragraph/sentence breaks (7000 char limit)
- embed_memories_batch(): groups messages by room, batch-embeds all texts to reduce Qdrant calls
- embed_issue_chunked(): auto-chunks long issue bodies
- embed_skill(): upgraded with auto-chunking via chunk_text
- TagEmbedInput struct for batch tag embedding
- embed_tags_batch() / search_tags() with project isolation
- ensure_collections() now creates embed_repo_tag collection
