docs: extract goget manpage to standalone troff source

README.md

@@ -271,13 +271,18 @@ just install      # go mod download
 just run          # run from source (development)
 just build        # go vet + gofmt check + build → bin/goget
 just test         # go test -race -count=1 ./...
+just man          # validate man/goget.1 with groff
+just install-man  # install manpage to ~/.local/share/man/man1/
 just uninstall    # remove build artifacts
+just uninstall-man# remove installed manpage
 ```
 
 ---
 
 ## Documentation
 
+- [`man/goget.1`](man/goget.1) — troff manual page (`man goget` after
+  `just install-man`)
 - [`docs/architecture.md`](docs/architecture.md) — components and request flow
 - [`docs/configuration.md`](docs/configuration.md) — config schema (TOML)
 - [`docs/api.md`](docs/api.md) — public Go library API