[nick2781]

Native application checks spend most of their time compiling: a completed Linux source run spent 26.2 minutes building and 2.4 minutes testing, with 29 cache hits from 409 compile requests. This change reduces unnecessary source-PR compilation and makes accepted application objects reusable across PRs and merge candidates.

• Select reviewed application check targets and let CMake build their dependencies. Missing/failed scope, public interfaces, unknown inputs, queue candidates and manual acceptance retain full coverage.
• Choose at most four compile jobs from detected CPU/memory, with separate conservative link pools. Compiler flags, Windows Debug settings, platform coverage, sanitizer checks and test timeouts are retained.
• Seed application compiler objects from trusted main, use compatible weekly snapshots and restrict queue uploads. Keep source-PR cache domains isolated and preserve normal compilation when optional caches are unavailable.
• Add a manual controlled cold/warm measurement, exact seed-availability checks and clear source/sample diagnostics. Document cache budgets and snapshot limitations in both languages, with concise contributor guidance.

Validation: 226 Node tests pass, including real CMake/Ninja target closures, compile/link concurrency, failure propagation, trust/fallback boundaries and existing workflow contracts. actionlint, full clang-format 18 and Nimbus build/link checks pass, including the combination with the actual #290 candidate.

Based on the accepted room integration in #290; the tested source already contains its actual accepted commit. Hosted native acceptance and controlled cold/warm timings remain required; no speedup percentage is claimed from local policy tests. This PR does not increase paid cache storage, delete remote caches or alter main protection.