feat(raft-log-replication): header contract — log model, callbacks, entry points (tasks 1.1-1.3)
Extend src/lib/raft/raft.h for the TLA+ log half (raft.tla logVars/leaderVars):
- raft_state_t: log_len, next_index[], match_index[] (no entry bytes stored —
terms via on_get_entry_term, bytes in the adapter); raft_config_t.initial_log_len.
- raft_callbacks_t: 4 REQUIRED log callbacks on_persist_entry, on_get_entry_term,
on_send_append_entries, on_truncate_from.
- Entry points + raft_append_result_t: raft_log_append (ClientRequest),
raft_send_append_entries (AppendEntries emit), raft_on_append_entries_request
(Handle + UpdateTerm-first), raft_on_append_entries_reply.
Concretized on_send_append_entries's varargs "entries handle" placeholder to an
explicit n_entries (0/1); design.md updated to match. Header compiles clean with
and without XCE_TESTING (-Wall -Wextra -fsyntax-only).
Rongsong Shen
6b5b201a64