Add reusable CI preparation operations

docs/consumers/delivery.md

@@ -7,6 +7,37 @@ The operation accepts historical lightweight and annotated tags, including a
 detached checkout, when the checked-out `HEAD` identifies the selected tag
 commit. It does not require the old remote `main` to match.
 
+## CI preparation
+
+Use `PrepareTaggedCheckout` when a disposable CI checkout must be verified
+against the commit that triggered the job. It fetches only the selected tag
+from the chosen remote (default `origin`), compares the peeled tag commit with
+the expected commit, and checks out that commit detached. Fetch or checkout
+conflicts are returned so the caller can replace or repair the workspace.
+Cancellation is returned to the caller; the operation does not publish a tag
+or hosted content.
+
+```go
+err := releasekit.PrepareTaggedCheckout(ctx, releasekit.TaggedCheckoutRequest{
+    RepositoryDir:  repositoryDir,
+    Version:        version,
+    ExpectedCommit: ciCommit,
+})
+if err != nil {
+    return err
+}
+```
+
+For binary profiles, call `PrepareBuildDependencies(ctx, repositoryDir)` after
+checkout preparation and before delivery. It runs `go mod download` with
+workspace discovery disabled and the available compatible local Go toolchain.
+The operation may use the network and updates the Go module cache while
+preserving the caller's proxy, private-module, credential, and cache settings.
+If checksums are missing, Go may update `go.sum`; see the
+[Go Modules Reference](https://go.dev/ref/mod#go-mod-download). Cancellation
+and command errors are returned. Page-only profiles do not need dependency
+preparation.
+
 ## Command line
 
 Add a Gitea destination to the profile: