Normalize process rewrite sources

[SonAIengine]

Summary

• strip trailing process words from process-query rewrite sources, e.g. rocks weathering process -> rock
• avoid over-singularizing non-plural ss words such as class
• record the post-rewrite DeepSeek 50-query follow-up and targeted source-cleanup note

Validation

• uv run ruff format --check src/synaptic/agent_tools.py tests/test_agent_tools.py
• uv run ruff check src/synaptic/agent_tools.py tests/test_agent_tools.py
• uv run pytest tests/test_agent_tools.py tests/test_agent_efficiency.py tests/test_agent_search_benchmarks.py tests/test_agent_loop_projection.py
• full MS MARCO SQLite deterministic smoke: how is soil created from rocks weathering reaches gold doc 7075449 at rank 1 with rewrites making soil rock pieces, small pieces of rock form soil