Summary

The make environment / ENVIRONMENT=true Docker/Podman dev shell, and the timberio/vector-dev:latest image it ran in, are no longer in active use. The image rebuilds on a weekly cron with no consumers, the Makefile threads a ${MAYBE_ENVIRONMENT_EXEC} wrapper through every build/test/bench/check recipe, and contributors have long since moved to native toolchains. This PR retires that path end-to-end and replaces the entry point with a contributor-friendly prepare.sh shortcut, hardened so it no longer surprises someone running it on a laptop. Continues the cleanup from #25410 and #25411.

What changes

• Makefile: removes the ENVIRONMENT_* variables, MAYBE_ENVIRONMENT_* macros, ENVIRONMENT_EXEC / ENVIRONMENT_PREPARE definitions, the four environment* targets, the ${MAYBE_ENVIRONMENT_EXEC} recipe prefix, and the "(Supports ENVIRONMENT=true)" section subtitles. Switches the VDEV macro to ?= so a caller-supplied VDEV (e.g. the pinned binary path exported by .github/actions/setup) wins over the local cargo vdev cargo-alias default.
• Dead target: drops build-graphql-schema; no graphql-schema binary exists in the workspace.
• CI: deletes .github/workflows/environment.yml (the weekly cron that built and pushed timberio/vector-dev:latest) and removes the /ci-run-environment review trigger and environment job from ci-review-trigger.yml.
• Docs: drops the "Using a Docker or Podman environment" section from docs/DEVELOPING.md and adds a pointer to scripts/environment/prepare.sh as the one-shot tooling install.
• Scripts: deletes scripts/environment/Dockerfile, entrypoint.sh, and setup-helm.sh (orphaned since 2022, pinned ~5-year-old kubectl/helm). The remaining scripts (bootstraps, binstall.sh, prepare.sh, install-protoc.sh) stay; they are still consumed by CI, cross/e2e/regression/tilt Dockerfiles, and the install docs.
• RFC 2685: marks rfcs/2020-05-25-2685-dev-workflow-simplification.md as archived and points readers at CONTRIBUTING.md / docs/DEVELOPING.md.
• prepare.sh workstation safety (folded in from enhancement(dev): make prepare.sh safer on workstations #25430): three CI-gated guards so the script no longer surprises a contributor on a laptop. (1) Skip the global safe.directory git config write outside CI; contributors own their checkouts. (2) Refuse to downgrade cargo tools the user has installed at a newer version than the pin (CI starts from nothing and still gets the pin; setting CI=1 forces it locally). (3) Skip the sudo ln -sf into the global npm bin outside CI; print a PATH hint pointing at the project-local node_modules/.bin instead.

How did you test this PR?

• make help renders cleanly with no stale targets.
• make -n test, make -n check, make -n bench resolve to bare cargo / $(VDEV) commands.
• env VDEV=/tmp/vdev make -n check prints /tmp/vdev check rust, confirming caller-supplied VDEV wins.
• make check-markdown passes.
• bash -n scripts/environment/prepare.sh and shellcheck are clean.
• Repo-wide grep for ENVIRONMENT=true, make environment, MAYBE_ENVIRONMENT_EXEC, INSIDE_ENVIRONMENT, timberio/vector-dev, scripts/environment/Dockerfile, scripts/environment/entrypoint, and setup-helm returns only the archived RFC.

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

• Related: chore(dev): remove cargo vdev test --container runner #25410, chore(ci): make regression/Dockerfile self-contained #25411
• Supersedes: enhancement(dev): make prepare.sh safer on workstations #25430 (folded in)