build: add -Wshadow -Wconversion -Wstrict-prototypes -O2

perf: reduce hash table from 65536 to 16 buckets

refactor: proper header with opaque API, modern C types

feat: case-insensitive lookups via ASCII lowercasing

portability: remove _GNU_SOURCE, replace strdup/strncasecmp

fix: check fgets return, single ht_get call, clean exit

refactor: simplify hash chains to unsorted prepend

perf: replace weak hash with FNV-1a

fix: plug memory leaks in ht_create, ht_newpair, and ht_set

cleanup

Merge pull request #9 from gotchacode/zig-port

Update POSIX feature definition in chatbot.c to enable GNU extensions

fix crash in latest llvm

Fix missing string.h include for cross-platform compatibility

feat: update benchmark