Add the OpenRouter catalog module

docs/release.md

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+# Catalog Release Procedure
+
+This repository releases source tags only. It has no generated artifacts.
+
+Before creating a semantic version tag, start from a clean, synchronized
+`main` branch. Confirm that no Go workspace, `replace` directive, or `vendor`
+tree is active, then run `GOWORK=off go test ./...`, `GOWORK=off go test -race
+./...`, `GOWORK=off go vet ./...`, `GOWORK=off go build ./...`, formatting,
+repository-hygiene, credential, and ordinary module-resolution checks.
+
+Create an annotated tag only after that validation succeeds. Do not create or
+move an existing tag. Push `main`, push only the selected tag, and verify the
+remote tag identifies the intended commit. Finally, from a temporary module
+with `GOWORK=off` and no replacement, resolve the published module version and
+verify the resolved version is the selected tag.