New:
- ai_hydro/citations.py: three-tier BibTeX citation registry
  Auto-collects data source citations per tool call; platform citations
  (aihydro, aihydro_tools) always included; plugin Tier 3 via register_plugin_citation()
- HydroSession.add_citations(), export_bibtex(), cite_all() methods
- _citations field persisted in session JSON

Fixes:
- Delete shadow session.py (was shadowed by session/ package, writing to wrong path)
- Fix .aihydrorules path in session/persona.py (was .clinerules)
- tools_docs.py docstring: .clinerules -> .aihydrorules
- mcp/helpers.py: _session_store() accepts tool_name= kwarg for auto-citation
- tools_analysis.py: all _session_store() calls pass tool_name=
- tools_modelling.py: adds HBV citation after model training
- tools_session.py: sync_research_context writes citations.bib; export_session uses export_bibtex()
- analysis/geomorphic.py, data/streamflow.py: various accuracy fixes