sampleplatform CI ("CI - linux" / "CI - windows" checks) is broken across all open PRs — stale baseline + infra failures

### Problem
The CI - linux and CI - windows checks (powered by sampleplatform.ccextractor.org) are failing on essentially every open PR right now, regardless of what the PR actually changes.

### Evidence
Checked 6 currently-open PRs (#2294, #2298, #2301, #2302, #2304, and one more) — none touching related code to each other and all show CI - linux and/or CI - windows as failing:

| PR | CI - linux | CI - windows |
|----|-----------|--------------|
| #2301 (EIA-608 encoding) | fail "Not all tests completed successfully" | fail same |
| #2302 (libpng ARM/CMake) | fail same | fail same |
| #2298 (EIA-608 CC3/CC4) | fail *"VM creation failed (ZONE_RESOURCE_POOL_EXHAUSTED_WITH_DETAILS). Please contact the administrator."* | fail "Not all tests completed successfully" |
| #2294 (Rust network framing) | fail *"Could not complete test, time limit exceeded"* | pending |
| #2304 (DVB subtitle fix, mine) | fail same as #2301/#2302 | fail/pending |

Three distinct failure modes visible:
1. *Stale comparison baseline: the "compared to test for commit ..." reference used across multiple different PR runs is 2feb09a (dated **2026-04-24), while current master HEAD is ba4a8390 (dated **2026-07-26) a **3-month gap*. Sample outputs/expected results have likely drifted in that window, producing failures unrelated to any given PR's actual diff (e.g. failures in Broken, CEA-708, General, Options, Teletext, WTV, XDS categories none of which relate to PR #2304's DVB-subtitle-only change).
2. *Cloud VM provisioning failures*: ZONE_RESOURCE_POOL_EXHAUSTED_WITH_DETAILS (PR #2298) the underlying cloud runner pool appears to be exhausted.
3. *Timeouts*: "time limit exceeded" (PR #2294).

### Suggested fix direction
- Update/automate the baseline comparison commit so it tracks current master instead of a fixed, aging reference.
- Investigate the sampleplatform cloud runner pool exhaustion / timeout issues (may be capacity/quota related).