chore: baseline snapshot — prior-session work + ha-consistency-invariants spec family

Pre-existing uncommitted work: ha-repl-hardening payload data plane (7.x),
heartbeat liveness fix (Req 1.3), connection-reuse ASAN fixes, doc cleanup.
New: ha-consistency-invariants umbrella (requirements/design/research) and
its four implementation sub-specs (specs generated via batch, cross-spec
review applied), steering roadmap + product.md Raft+CP decision.

src/lib/meson.build

@@ -173,6 +173,7 @@ libxce_test_src = ['testsuite/test.c',
                    'testsuite/test_libxce_retry.c',
                    'testsuite/test_netio_on_connected.c',
                    'testsuite/test_raft.c',
+                   'testsuite/test_wal_wire.c',
                    'raft/raft_sim.c',
                   ]