fix(docs): pin gomarkdoc repository URL flags for deterministic output

CI run 25607949051 failed on the codegen-clean diff check. gomarkdoc
auto-detects the GitHub repository URL from local git config — locally
on a full clone with origin set, it generates source-line links
([func Foo](https://github.com/.../blob/main/...#L4590)); on the CI
runner's fresh checkout, the remote info isn't available the same way
and gomarkdoc emits unlinked headings (## func Foo). The committed
docs (with links) and CI-regenerated docs (without links) diverged,
breaking the gate.

Pin the URL, branch, and path explicitly via gomarkdoc flags so output
is identical regardless of where it runs.

Makefile

@@ -82,7 +82,11 @@ DOC_PACKAGES := \
 
 docs:
 	@which gomarkdoc > /dev/null || (echo "installing gomarkdoc..." && $(GO) install github.com/princjef/gomarkdoc/cmd/gomarkdoc@v1.1.0)
-	gomarkdoc -o 'docs/reference/{{.Dir}}.md' $(DOC_PACKAGES)
+	gomarkdoc \
+		--repository.url=https://github.com/lukaszraczylo/go-telegram \
+		--repository.default-branch=main \
+		--repository.path=/ \
+		-o 'docs/reference/{{.Dir}}.md' $(DOC_PACKAGES)
 
 docs-check: docs
 	@git diff --exit-code docs/reference/ || (echo "docs/reference/ is stale — run 'make docs' and commit" && exit 1)