[CI] (.github/workflows, docs/ci, scripts/ci): fold the strict split lane into the dual-block run

- on the disaggregation branches the dual-block census step's first run leaves MOBILEGL_IPC_ROLE_SPLIT_STATE at its default, which makes its environment the strict split lane's; the step proves per entry that strict, the dual block and run-ahead resolved on, and makes the strict lane's checks on that run
- junit_tally.py --select-from/--write-selected carves the integration-split part out of dualblock.xml as strict-split.xml, every name exactly once (exit 3 otherwise); tests in tcp_lane_tools_test.py
- 'Strict split lane' runs on dev only; 'Magma split lane' is skipped when the dual-block run proved its defaults, since that run covers the label in the same environment; a changed default reruns the census with the knob set

docs/ci/ci-cleanup-log.md

@@ -50,6 +50,8 @@ them wrong.
 | 2026-10-17 | `Transport A/B (monolith vs inproc)` (skip-census lanes `arm-monolith`, `arm-inproc` now optional) | Test / `integration-split` | with `build-linux` reused it repeats the integration job's two legs on the same library (79 paired runs, no one-sided red) | the integration legs; `Transport and default-knob resolution check` now reads 'Split lanes' own run and proves, from every passed entry's client log, strict=0, role-split-state=1 and run-ahead=1 unless pinned (`split_log_paths.py ipc-config`); A/B still runs when a default differs or the build is not reused |
 | 2026-10-17 | `Unit tests on the split runtime` (skip-census lane `unit-split` now optional) | Test / `integration-split` | with `build-linux` reused the test job runs the same unit lane on the same build (182 paired runs; the one recurring one-sided red was a fixed test race) | the test job, which now carries `MOBILEGL_ITEST_REQUIRE_GPU=1` and `libegl-mesa0` on the three branches; the strict unit step is unchanged |
 | 2026-10-17 | the integration-gpu entries that pin their own `MOBILEGL_TRANSPORT` (804 inproc, 1446 spawn, 131 monolith) and the 12 `TcpServer` fixture entries only they need, in the inproc-acceptance leg (both passes) | Test / `integration` (inproc-acceptance) | their pin overrides the only variable the two legs differ in, so they ran identically in both (173 paired runs; the one one-sided red was a port bind fixed by cde6512b) | the monolith-control leg, which runs them on every branch; `transport_pinned.py` proves per run that the trimmed selection lost exactly that population (else the leg runs everything) and that the monolith-control leg ran every one; skip census: the monolith-control lanes list their own names and the inproc-acceptance lanes drop the pinned ones |
+| 2026-10-17 | `Strict split lane` on the disaggregation branches (dev keeps it) | Test / `integration-split-strict` | with the role-split state defaulting on, its environment equals the dual-block census lane's, whose entries are a superset (31 paired runs after the flip, never red only in the strict lane) | the dual-block step's first run leaves the knob at its default, proves per entry from its client log that strict, the dual block and run-ahead resolved on (`ipc-config`), writes the integration-split part of its JUnit as `strict-split.xml` (every name exactly once, `junit_tally.py --select-from`), and makes the strict lane's checks on it (hard green, two-sided marker census, StrictArming ran); a default that changed reruns the census with the knob set |
+| 2026-10-17 | `Magma split lane (strict, dual-block)` on the disaggregation branches when the dual-block step proved its defaults | Test / `integration-split-strict` | the dual-block census run covers the `integration-magma-split` label in the same environment | the dual-block census run |
 
 ## Kept after investigation