I would like to know where I can find XSD file for CentraSite pages (<page model="…). I would like to use that file in Eclipse to get tooltips informing me what tags/attributes are available during page editing (intellisense style).
CentraSite currently uses a custom UI technology (used to be called Application Designer) for generating pages. That UI technology uses so-called editor*.xml files to define and constrain UI elements and they are nothing like the XSD files you are after.
You can see those xml files at \profiles\CTP\workspace\webapps\PluggableUI\cis\config