fix: close bug-847 (un-ignore fixed reproducer), confirm bug-1307 fixed via soak

bug-847 (catch-up WAL batch drops payloads across capnp segment boundaries):
its purpose-built RED reproducer, test_wal_batch_roundtrip_large_payloads
(14 entries x 872-byte payloads, 12.2KB total, genuinely spans multiple
4096-byte capnp segments per capn-malloc.c's create()), was still
TEST_IGNORE_MESSAGE'd. Un-ignoring it and running under ASAN with leak
detection: clean pass, byte-exact payloads, zero leaks, 2/2 runs. Traced the
vendored c-capnproto far-pointer machinery (write_ptr/capn_setp in capn.c)
to confirm the cross-segment struct->Data reference path is correct by
construction — whatever regressed this already got fixed elsewhere (library
bump or an incidental request.c change); the ignore was just never removed.
No production code changed.

bug-1307 (task-5.7 election-jitter data-safety regression: 7 divergences +
4 job losses over 6 chaotic rounds): re-ran the exact reproducing scenario
(6-round chaotic soak, real ext4, ASAN binaries) — 21 jobs, 0 divergence,
0 job loss, clean PASS. Confirms the raft-ha-core-safety Phase 5 work
resolved it.

Both bugs were the last 2 of the 7 flagged in the prior staleness sweep;
all 7 are now closed (6 were already fixed and undetected, 1 needed the
test un-ignored).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SDWVNQLKxqTVHh42cH7rV3

src/lib/testsuite/test_wal_wire.c

@@ -104,10 +104,6 @@ static void test_wal_batch_roundtrip_large_payloads(void)
      * this TEST_IGNORE line when bug-847 is fixed and assert the payloads
      * survive. Decisive evidence: this fails "Expected 872 Was 0" while the
      * 2-entry round-trip above passes. */
-    TEST_IGNORE_MESSAGE(
-        "bug-847: catch-up batch drops payloads across capnp segments — "
-        "un-ignore when fixed");
-
     enum { N = 14, PSZ = 872 };
     wal_catchup_entry_t  e[N];
     wal_catchup_entry_t *entries[N];