#3071 Docs: extension push dry-run reference and how-to need the registry checks, API-call list and content hash from Lab #3016

What changed

Lab #3016 makes swamp extension push --dry-run run the registry-side checks (authentication, collective membership, reserved collective, version exists across all channels) read-only when credentials are present, listing each result with the real push's wording and exiting non-zero on a failure; without credentials it lists which checks it could not run. The dry-run summary lists the API calls actually made (registry, OSV, npm) and prints the content hash. The swamp skill gains a recipe to reproduce the CI publish layout (swamp repo initialised inside the extension directory).

Pages to update

• content/manual/reference/extensions/publishing.md (around lines 97-138): the --dry-run flag description says build and validate locally, do not upload; step 12 says upload is skipped under --dry-run; the Output (dry run) sample lacks the registry checks block, the API calls block and the content hash line.
• content/manual/how-to/extensions/create-and-publish.md (around lines 234-271): the dry-run walkthrough should mention that a dry run now refuses an already-published version or a collective the account is not in, and show the CI-layout recipe for authors who want the same content hash as a CI publish.

Suggested content

Describe the four checks and the three outcomes (passed, failed, not run with reason), the apiCalls, registryChecks and contentHash fields in the JSON summary, and the recipe: cd into the extension directory, run swamp repo init --quiet --tool none if there is no .swamp.yaml, then swamp extension push manifest.yaml --dry-run --json.