How could one serve maps (tiles in wherever format possible) within a Android device to be consumed by an offline webmapping app also accessed within the device's browser?
Your webmapping offline code will be located in Assets folder.
You can put your tiles (XYZ or TMS) in a folder hierarchy inside Assets, too, and access your tiles via relative paths.
You really don't need a web server, the same way you don't need it to import a JS file into your HTML page.
There are a few options using TileMill/Mapbox/MBTiles... Not html5 though. You may want to explore other options for android than html5!!
MBTilesDroidSplitter : https://github.com/djcoin/MBTilesDroidSpitter
Locus : http://www.locusmap.eu/