Workflow contract helpers match commented-out lines in run: blocks

multiline_run_blocks in xtask/src/workflow_contract.rs keeps shell comment lines when it flattens a run: | block. Every contains assertion built on it can therefore be satisfied by a line that is commented out and has no effect on the runner.

Why it matters

This is not only theoretical. Commenting out the two exports in the Windows lifecycle step:

# $env:ROCM_CLI_BINARY = "$targetDir\release\rocm.exe"
# $env:ROCM_CLI_ROCMD_BINARY = "$targetDir\release\rocmd.exe"

leaves ci_windows_lifecycle_lane_reuses_the_binaries_it_built green, even though it pins the full assignment strings — the commented line still contains them. Commenting two lines out is exactly what someone bisecting a CI failure does, so the guard is weakest in the situation it exists for.

The same class defeats the fail-fast Test-Path/throw assertion added in #342.

Four tests share the helper: self_hosted_prebuilt_e2e_lanes_export_rocmd, nightly_prebuilt_e2e_lanes_export_rocmd, and the two ..._enable_test_hooks tests.

Also in scope

assert_prebuilt_e2e_lanes_export_rocmd pins the full assignment for rocmd but only the bare variable name for rocm, so $env:ROCM_CLI_BINARY = "$targetDir\debug\rocm.exe" passes for e2e-selfhosted.yml and nightly.yml. #342 closed that asymmetry in its own new test and deliberately left the shared helper alone; both reviewers agreed the helper fix belongs in its own change. Doing both together is the tidier move.

Proposed fix

Drop comment-only lines when building the block, then pin the rocm assignment in the shared helper.

One thing to check before landing: assert_prebuilt_e2e_lanes_enable_test_hooks asserts a block contains e2e-test-hooks. Confirm no lane satisfies that only via a comment, or stripping comments will turn a passing test red for the right reason but at an inconvenient moment.

Read xtask/src/workflow_contract.rs, starting with multiline_run_blocks and assert_prebuilt_e2e_lanes_export_rocmd. Run the four named workflow-contract tests, including the enable-test-hooks checks, and inspect the referenced Windows and nightly workflow blocks. Done means commented-out lines cannot satisfy the assertions and the intended rocm assignment is checked without breaking valid lanes.