MUL-6697: enforce runtime access on task claims (#7571)

* fix(tasks): enforce runtime access on claims

Co-authored-by: multica-agent <github@multica.ai>

* fix(tasks): settle invalid runtime claims explicitly

Co-authored-by: multica-agent <github@multica.ai>

* test(tasks): cover runtime owner claim mismatch

Co-authored-by: multica-agent <github@multica.ai>

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Co-authored-by: Sol-Boy <sol-boy@multica-ai.local>
Co-authored-by: multica-agent <github@multica.ai>