ci(windows): bound installation separately from runtime qualification

The Windows runtime qualification job is cancelled during dependency installation before either real Windows assertion executes. At commit 5c16100b246808be5603dc21c744aff6517d58cd, job 105383068897 carries GitHub’s annotation: “The job has exceeded the maximum execution time of 15m0s”. Installation occupied 837 seconds; identity storage and normal-user junction staging were skipped. This leaves the Windows qualification incomplete, not failed assertions.

A previous runtime job installed the same dependency inputs in 430 seconds; the same-head Windows browser-security job installed successfully in 449 seconds. The lockfile, manifests, Bun configuration and patches did not change between those runtime attempts. The cause of the slow installation remains unestablished.

Bounded correction: allow 30 minutes for this qualification job, with an explicit 20-minute installation deadline. Preserve pinned toolchains, frozen installation, generated keyword ordering and both real Windows assertions. Add no retries or success bypass. If installation reaches the new limit, investigate its process/disk behavior rather than raising the limit again.

Acceptance: source/YAML validation and existing focused workflow contracts pass, followed by an exact-head hosted Windows run that completes both real assertions and uploads its evidence. The full combined integration gates remain required. This changes only the hosted dependency-installation budget, not the runtime restart watchdog tracked in #31535.