ci(installer): cover all greenfield execution arms

docs/scratchpads/1050-install-state-machine-red-fixture.md

@@ -151,3 +151,12 @@ Denominator corrections were sent to and accepted by the lane lead before implem
 - Requirement 5 adds a pipeline-level instrument above the three per-case invocations. Expected names are derived from the manifest, markers are scoped by pipeline+workflow run, and each marker is written only after that exact per-case verifier succeeds. Every producer depends on initialization; the final step depends on the complete case/contract matrix, runs after success or failure, and requires exact expected/actual set equality rather than count equality.
 - Measured firing controls: skipped arm `3/2` rc1; count inflation `3/3` rc1 with one missing and one unexpected name; stale re-initialized run `3/0` rc1; exact set `3/3` rc0; future manifest case `4/3` rc1. Codex review found and blocked two independent defects: first the missing `depends_on` graph, then comment lines being parsed as case names. Both were accepted; dependency edges are regression-asserted, blank/comments are excluded, and the focused test now consumes the production manifest directly. Final Codex code re-review APPROVE confidence 0.94 and security re-review risk NONE confidence 0.96, both with zero findings. Woodpecker strict lint, Bash syntax, ShellCheck, focused/full installer tests, typecheck, lint, Prettier, and diff check pass.
 - Full evidence: `docs/reports/verification/1050-c1-fix-round/10-round4-case-coverage.txt`.
+
+## Round 5 — arm coverage and checkout purity
+
+- Reviews 110/111 identified two blockers at `f33bd0da`: the three-case set could not represent the fourth `greenfield-remote-installer-contract` arm, and the root `.greenfield-case-state` directory was included in checkout fixture archives. The expected-RED manifest, per-case verifier, detector, and #869 remain fenced.
+- RED controls: with all three cases complete and no remote-arm identity, the old gate returned rc0 at `cases_defined=3 cases_executed=3`; the exact fixture tar selector archived `.greenfield-case-state/remote-arm.ran` once.
+- The checker is generalized across exact `cases` and `arms` dimensions. A new explicit four-arm declaration includes the remote contract; all four arms mark only after successful per-case verification. With the remote omitted, cases remain 3/3 rc0 while arms report 4/3 rc1 and name `greenfield-remote-installer-contract` as missing.
+- State moved beneath `.mosaic-test-work/greenfield-execution-coverage`, which the existing checkout selector excludes. The regression control proves a non-excluded root marker is archived while no `.mosaic-test-work` path is archived.
+- Final review: Codex code APPROVE confidence 0.93 and security risk NONE confidence 0.96, both with zero findings. Full installer tests, typecheck 45/45, lint 25/25, format, Bash syntax, ShellCheck, Woodpecker strict lint, and diff check pass with 11G free before/after.
+- Full evidence: `docs/reports/verification/1050-c1-fix-round/11-round5-arm-coverage-and-purity.txt`.