New test coverage:
- Cache layer: LocalCache (LRU, TTL, eviction), NullCache, PrefixCache, StringCacheAdapter
- Database: FledgeMariaDbConnection, FledgeMySqlConnection (isMaria), FiberDB edge cases
- PDO: FETCH_CLASS mode, named params, buildExecuteParams, Postgres placeholder edge cases
- HTTP: body copying, timeout mapping, on_stats callback, body size limit
- Redis: flattenParameters, pairsToAssociative, FledgeRedisPipeline queue/chain
- Connectors: charset/collation config, getSqlMode, connect_via

Also renames remaining Amphp-prefixed test files to Fledge prefix.