docs: document GitHub repo creation flow

docs/github-repository-creation.md

@@ -0,0 +1,31 @@
+# GitHub repository creation
+
+StackForge does not create GitHub repositories by default. The `init` command only plans GitHub repository creation when `--github-create` is present.
+
+## Dry-run-first flow
+
+Run with `--github-create` to print the planned `gh repo create` command in the JSON output without executing it:
+
+```bash
+pnpm dev init oss-cli my-tool --github-create
+```
+
+The default GitHub repository visibility is `private`. Use `--github-visibility public` only when you intentionally want a public repository:
+
+```bash
+pnpm dev init oss-cli my-tool --github-create --github-visibility public
+```
+
+After reviewing the printed `github.command`, rerun with `--github-execute` to create the repository through the GitHub CLI:
+
+```bash
+pnpm dev init oss-cli my-tool --github-create --github-execute
+```
+
+## Safety rules
+
+- Without `--github-create`, StackForge reports `github.mode` as `noop` and never calls `gh`.
+- `--github-create` defaults to `github.mode: "dry-run"` for the GitHub command.
+- `--github-execute` requires `--github-create` so repository creation is always explicit.
+- `--github-execute` cannot be combined with `--dry-run`.
+- GitHub creation uses the installed `gh` CLI and any authentication already configured for it.