[CI] (.github/workflows, docs/ci, MG_IntegrationTest/Harness, scripts/data): reuse build-linux for split

- build-linux and build-linux-split each probe the other's configure line with build_fingerprint.py on their own runner (disaggregation branches only); when it matches, build-linux-split skips its compile and the split consumers take build-linux's runtime and library
- the consumers red when build-linux-split skipped but build-linux's guard did not agree, or when the link ratchet, now also run in build-linux, did not pass; a difference falls back to the old two builds, and dev is unchanged apart from the consumers also waiting for build-linux
- the transport resolution check moves after 'Split lanes' and proves the IPC defaults from each passed entry's client log (split_log_paths.py ipc-config, canned tests); with both proven, Transport A/B and the non-strict split unit run are skipped as repeats
- the test job carries REQUIRE_GPU and libegl-mesa0 on the three branches; skip census: arm-monolith, arm-inproc and unit-split become optional rows

docs/ci/ci-cleanup-log.md

@@ -46,6 +46,9 @@ them wrong.
 | 2026-10-17 | `Negative control A (server-side read)` and `Negative control B (omitted stamp)` | Test / `integration-verify-split` | the first re-ran the two VerifySplitReadCorrupted entries the lane had just run and grepped what they already assert in-test (at least two where=read reports in the server half); the second re-ran with the pair the in-lane VerifySplitPoisonOmitted entries already pin, and accepted any red | `Verify-split control entries`: `--require-entry-passed` on VerifySplitArming, VerifySplitCorrupted, VerifySplitReadCorrupted and VerifySplitPoisonOmitted of both backends |
 | 2026-10-17 | the pre-flip arm of `Strict split lane` (red-by-design while `kMGPipeP5eRunAheadReady` was false) and the "GREEN with rows outstanding" rule of `Dual-block census lane` | Test / `integration-split-strict` | dead: the constant is true, and `dualblock-expected-fatals.txt` has no rows, so neither branch could run | the hard-green arm and its two-sided marker census, and the empty-census rule (rows == 0 requires ctest success), both kept |
 | 2026-10-17 | `scripts/ci/tcp_log_forwarding_control.py` | none | no caller outside the archived planning notes | none needed |
+| 2026-10-17 | the compile of `build-linux-split` on the disaggregation branches (when its guard proves the configurations equal) | Test / `build-linux-split` | it built the library `build-linux` builds there, from a configuration that differs only by the benchmarks (211 paired runs never disagreed); it delayed every split consumer by up to 9 minutes | `build_fingerprint.py` guards in both build jobs (cache, compile commands, link statements, CTest files, toolchain; benchmarks excluded); the consumers take `build-linux`'s artifacts and red if `build-linux`'s own guard disagrees; the link ratchet runs in `build-linux`; on any difference `build-linux-split` builds as before, and dev is unchanged |
+| 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 |
 
 ## Kept after investigation