feat: HTTP server for exporting Arborix bundles

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`.

.gitignore

@@ -6,6 +6,7 @@
 /Dockerfile
 /config.dhall
 /result
+/result*
 .aider*
 WD
 bin/