docs(libxce-failover): log bug-609 (known-dead EINVAL) + record 6.2 live-E2E partial status

.kiro/specs/libxce-failover/tasks.md

@@ -111,3 +111,4 @@
 - 5.2: `XCECLI_FF_CALL` macro (single-shot, NO retry loop/backoff/budget): lock → if known-dead (xcecli_ff_needs_reconnect = ctx.state==XCE_CTX_ERR) one rotate+recover → one send → unlock. Applied at the 3 wire chokepoints xcecli_notify/heartbeat/nop (notify_* delegate to xcecli_notify). wakeup/try_wakeup are LOCAL-only (cbuf_tryput own wbuf, no wire send) so correctly NOT wrapped.
 - 5.3: `fill_redirect_reply(xce_reply_t*, const ha_state_t*)` (non-static, join.c) sets redirect_host=ha.primary_host + redirect_port=(uint16_t)ha.primary_port; called ONLY on the E_XCE_REDIRECT branch before xce_reply. Audit: join.c is the SOLE E_XCE_REDIRECT emitter. NOMASTER path unchanged (8.2). host alias (no copy) safe: ha lives cluster-lifetime, xce_reply serializes synchronously. New test_join_redirect.c registered in controller_test.c + meson.build.
 - 6.1: full lib suite green (161 tests). All 14 reqs (2.4,2.5,3.2,3.3,4.1-4.5,5.2,6.2,6.3,8.3,8.4) map to genuine passing tests. Gap-filled 6.3 with `test_decide_jitter_staggers_many_clients` (64 distinct-seed carriers → staggered delays, anti-thundering-herd). No production bugs found.
+- 6.2 (LIVE E2E — partial): Live 3-node cluster (deploy-ha.sh) was brought up and DID elect a primary; killing the primary triggered server-side failover (ctrl-2 self-elected term=2). The run REPRODUCED the original `Invalid argument` client bug → root-caused + FIXED (bug-609, known-dead-ctx override) + regression unit test added. The clean within-session client transparent-recovery could NOT be visually demonstrated in this sandbox (background controller processes are reaped between tool calls; nix runtime env needed for backgrounded procs; lib build cleans the controller binary). RECOMMEND final visual confirmation in a stable env: build all, `/xce-deploy-ha localhost:9991 localhost:9992 localhost:9993`, run xce_test (set masters / client / jobsub / joblist), kill the primary, confirm joblist reports cluster-not-ready then transparently recovers (no EINVAL).