Fix test client refactor: broken includes, typos, and structural bugs

- Rename include/lib.h to include/toastyfs.h, add -Iinclude to build
- Fix build.sh: replace deleted blob_client.c with random_client.c
- Fix src/client.c: wrong include (client_lib.h), add missing STEP_FETCH_CHUNK
  enum, add missing struct fields (bucket, key, blob_size, content_hash,
  error, file_size, phase_time), fix TRANSFER_WAITING->TRANSFER_PENDING,
  fix begin_transfers() wrong variable refs, fix reap->resp typo,
  fix resp.size check inversion, fix state->tfs in process_events,
  fix tfs->transfer->tfs->transfers, fix tfs->phase->tfs->step,
  fix function name typos in toastyfs_get_result, fix async_put->async_get
  in toastyfs_get, fix ReplyMessage->RequestMessage in async_delete,
  fix put_result/delete_result return types, fix wait_until_result,
  add leader_idx() and toastyfs_alloc(), add missing MessageHeader casts
- Fix src/random_client.c: randm_client.h typo, addrs[i]->addrs[num_addrs],
  use toastyfs_alloc() for opaque type, fix tfs->state->tfs refs
- Fix src/random_client.h: wrong include guard names
- Fix src/main.c: replace deleted client.h/blob_client.h with
  random_client.h, update all client spawn configs to use RandomClient

https://claude.ai/code/session_018MRQTdAZoBCXJZgdP4U6V6

src/random_client.h

@@ -1,5 +1,7 @@
-#ifndef BLOB_CLIENT_INCLUDED
-#define BLOB_CLIENT_INCLUDED
+#ifndef RANDOM_CLIENT_INCLUDED
+#define RANDOM_CLIENT_INCLUDED
+
+#include <toastyfs.h>
 
 #include "tcp.h"
 #include "basic.h"
@@ -22,4 +24,4 @@ int random_client_tick(void *state, void **ctxs,
 
 int random_client_free(void *state);
 
-#endif // BLOB_CLIENT_INCLUDED
+#endif // RANDOM_CLIENT_INCLUDED