`fetch-depth: 0` means fetching all heads and tags.

Except for non-development that runs build only.

The inputs context is only populated for workflow_dispatch and
workflow_call, so referencing it on push, pull_request, or merge_group
relies on undefined behaviour. Short-circuit on github.event_name so
non-dispatch runs always pass false to the reusables.

SIMPLER_ALERTS_URL always fires on failure so developer-facing CI
(PR, push, merge_group, manual dispatch) surfaces breakage in the
ruby-core channel. notify-release-channel additionally routes to
SNAPSHOT_SLACK_WEBHOOK_URL for the daily snapshot dispatcher and
future draft-release callers, with the same payload schema as before
except commit now comes from github.sha.

The step force-removed $HOME/.gnupg between Tests and Diff stats of
HOME, but the original cause for the directory persisting was never
identified. Remove it and observe whether the HOME diff still passes.

power_assert was allowed to fail on master/4_0 by passing it through
this input. The allow-list belongs in tool/test-bundled-gems.rb now
that the tool ships in the same repo as the workflow.

The legacy mode (vs2022 + vcvars 14.2) is no longer exercised, so
collapse the conditional matrix into the modern 2022 / 2025-vs2026
pair and remove the now-dead setup-env (legacy) step.

GitHub Actions schedule triggers only fire from the default branch, so
the daily run defined in tarball-test.yml never executed on ruby_3_3,
ruby_3_4, or ruby_4_0. Move the cron into a new dispatcher workflow
that calls workflow_dispatch on each branch via a PAT.

Cherry-picking tarball-test.yml to maintenance branches previously
required editing six places (four archname literals, branch-label, and
the Materialize step). Route everything through env.BRANCH on the
tarball job and expose it via outputs so downstream reusable workflow
calls reference needs.tarball.outputs.branch. Maintenance branches now
flip one line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>