Add detail_level and max_flows to get_affected_flows

get_affected_flows_tool was the only tool in the review chain without
detail_level, and it had no result bound. Every flow carries a full
steps list, so a 75-file change set returned a 247k-token response in
the middle of the documented minimal-first workflow.

detail_level="minimal" strips flows to per-flow metadata (name,
criticality, depth, counts). max_flows bounds the list (default 50,
0 disables); total always reports the untruncated count and truncated
flags the cut, mirroring the impact-radius truncation contract.

Fixes #849