Introduces a read-only HTTP server (WAI/Warp) backed by the content
store, exposing three bundle-export endpoints:
- GET /bundle/name/:name — export by stored term name
- GET /bundle/hash/:hash — export by full Merkle hash
- GET /terms — plain-text listing (debug)
Also adds `tricu server` (aka `--serve`) CLI mode, move `resolveExportTarget` /
`namesForHash` / `looksLikeHash` out of `Main.hs` into `ContentStore.hs`,
and cleans up unused exports and imports across `FileEval.hs` and `Wire.hs`.
