ci: use the shared pull request, release and autoupdate workflows (#19)

* ci(workflows): migrate to shared go-pr and go-release workflows

Replace the generic vet, staticcheck, govulncheck, gosec, test and release jobs with the shared go-pr and go-release workflows.
Keep the codegen-clean and audit jobs in ci.yml. Add an examples build job and the ci-success aggregator there.
Add autoupdate.yaml from the shared go-autoupdate workflow.
The release job now runs only on Go source changes and on manual dispatch.
The dry-run input and the Bot API note in the tag message no longer exist.

* ci(release): gate release on repo checks and export Bot API version

Move the codegen-clean, audit and examples jobs into the reusable checks.yml workflow. The ci.yml and release.yml workflows both call it.
The release job now needs the checks job. A failed or cancelled check blocks the release.
Add workflow-prepare.sh. It appends BOT_API_VERSION to GITHUB_ENV so the GoReleaser header shows the Bot API version.
The script does nothing when GITHUB_ENV is unset.

* ci(regen): name release.yml in the merge step comments

The release now runs from release.yml. The comments still named ci.yml as the workflow that cuts the release.

.github/workflows/autoupdate.yaml

@@ -0,0 +1,20 @@
+name: Autoupdate go.mod and go.sum
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: "0 3 * * *"
+
+permissions:
+  contents: write
+  actions: write
+  pull-requests: write
+  security-events: write
+
+jobs:
+  autoupdate:
+    uses: lukaszraczylo/shared-actions/.github/workflows/go-autoupdate.yaml@main
+    with:
+      go-version: ">=1.25"
+      release-workflow: "release.yml"
+    secrets: inherit