A rutted bike path whose disrepair caused the death of a lifelong Bay Ridgite has completed the first lap of a $12-million restoration.The Shore Parkway bike path — one of only three greenways in Brooklyn — has been converted from a pothole-riddled obstacle course into a smooth conduit from 92nd Street to the Verazzano-Narrows Bridge. The remainder of the waterfront path — from 69th to 92nd streets — will be rehabilitated by the beginning of July.The Parks Department, which maintains the path, was blamed last year after Keith Alexander Bonanno, 41, a body artist and rock guitarist, lost control and hit his head on the guardrail, suffering a fatal blow. The path has been closed since last summer for emergency repairs, which were funded with grants from Rep. Vito Fossella (R-Bay Ridge) and state Sen. Marty Golden (R-Bay Ridge). While many residents are thrilled that the repairs are almost finished, others wish the improvements had been made years ago. "The maintenance of that particular path had not been so great," said David Snetman, bicyclecampaign coordinator for Transportation Alternatives. "People put [bike paths] in and just sort of neglect them. And then it costs millions to replace, rather than hundreds of thousands to maintain." The late cyclist's mother agrees. "A little late, isn't it?" said Barbara Bonanno. "It took my son's life to get it done."