solang-0001: add_external_functions emits_events Vec::contains O(F×E²) MEDIUM
src/sema/external_functions.rs:93-103 — dedup accumulator Vec uses linear scan
for each event per function; fix: IndexSet (already a dependency) for O(1) dedup
tor/bitcoin/transmission/libtorrent/solc: CLEAN markers added after full scan
Tor: nodes_have_common_family_id F=1-3 IDs, O(N×F²) ≈ O(9N), not scalable issue
Bitcoin: TxGraph/sets throughout, no linear scan in hot paths
Transmission: bitfields for piece tracking, sorted binary search for string table
libtorrent: sorted vectors with lower_bound, DHT uses binary search on results
solc: unordered_set/set throughout OverrideChecker, SMTEncoder, FunctionCallGraph
