ci(workflow): avoid redundant builds and preserve active checks

[nick2781]

CI currently repeats the full matrix after a protected merge and cancels active runs when a newer push enters the same concurrency group. Dependency archives are also saved only after project tests, so later failures can discard already built dependencies.

Remove the redundant CI main-push trigger, preserve active per-PR/ref runs, and save existing vcpkg archives immediately after successful configuration. PR, merge-group and manual checks remain intact, as do all matrices, required checks, fatal build/test behavior, permissions, cache identities and timeouts. Documentation publication keeps its separate main-push workflow. Update bilingual guidance, merge-queue badges and the oldest-unblocked-PR scheduling rule.

Validation source: e89481d02257e55784f9c7c63602177752b2938f, tree 6602fdb154343c6f74e750265ebf35b5ebe934a4, incorporating accepted main 6556aaf882398823ceeeedf21bf6ee6d23e2f5f9.

• All 43 dependency-free CI/README tests pass, including cache placement, failure/cancellation/missing-result gates and workflow concurrency checks.
• The nine-file patch is unchanged from the reviewed proposal; accepted layout, runtime, architecture and plugin guides are preserved.
• Structured workflow comparison and whitespace checks pass. Required hosted checks and the actual merge-queue candidate must still pass before acceptance.

GitHub may replace an older pending run within a concurrency group; this is not a global FIFO scheduler. Cache ref isolation is unchanged. These workflow-only changes do not claim a new native or performance test result.