Kahai Street Kitchen   Once you taste the food at Kahai Street Kitchen, you won't care about the lack of decor, the scuffed linoleum, the out-of-the-way location. Because it's brok' da mout' — and it's not what you'd expect: seared 'opakapaka in lemon-butter-caper sauce. Tea-smoked duck breast. Seafood paella. Chicken saltimbocca. Osso bucco-style short ribs. The people are nice. Really nice: They learn your name and use it. They double-check that they are giving you the right order. They talk story. They smile. Partners Nao Iwata, Charlie Chintam and Ken Furuta are all food-business veterans. Their goal: "semi fine-dining food at platelunch prices."  237 Kalihi St. 845-0320. 10:30 a.m.- 1:30 p.m. Mondays-Fridays. Cash and local checks only. Ward Centre, 1200 Ala Moana. 596-7488. 8 a.m.-9 p.m. Mondays- Thursdays; 8 a.m.-10 p.m. Fridays- Saturdays; 8 a.m.-5 p.m. Sundays. AX, DC, DS, JCB, MC, VS. No checks.