docs: enhance release flow documentation and add version command to CLI

- Updated AGENTS.md and README.md to clarify the automated release process using release-please and GoReleaser.
- Added a version command to the envc CLI to display build metadata.
- Included CI/CD details in README for better understanding of testing and release automation.

docs/asr/ASR-0009-ci-cd-and-automated-semver.md

@@ -0,0 +1,65 @@
+# ASR-0009: CI/CD pipeline and automated semantic versioning
+
+## Context
+
+ASR-0008 only covered GitHub presentation and the initial manual tag of `v0.1.0`.
+The project needs continuous verification on every PR and a release flow that does
+not require humans to bump version strings. The source tree must stay free of
+version literals (the CHANGELOG aside) so that `go install …@latest` and GoReleaser
+artefacts agree on a single source of truth: **git tags**.
+
+## Decision
+
+1. **Test pipeline** (`.github/workflows/test.yml`): matrix of Go `1.22`, `1.23`,
+   and `stable` on `ubuntu-latest` plus one `stable` run on macOS and Windows,
+   with `go test -race -shuffle=on -count=1 -coverprofile=coverage.out`. Coverage
+   is uploaded to Codecov from the Linux `stable` leg only. `go mod tidy` is
+   enforced via `git diff --exit-code`.
+2. **Lint pipeline** (`.github/workflows/lint.yml`): `go vet` plus
+   `golangci-lint@v6` using the repo's existing `.golangci.yml`.
+3. **Automated SemVer** (`.github/workflows/release-please.yml` +
+   `release-please-config.json` + `.release-please-manifest.json`): Google's
+   [release-please-action](https://github.com/googleapis/release-please-action)
+   in `release-type: go` mode parses [Conventional
+   Commits](https://www.conventionalcommits.org/) since the previous tag and
+   opens a "chore: release vX.Y.Z" PR that edits `CHANGELOG.md` and the
+   manifest only. Merging the PR creates the git tag. The manifest is seeded
+   with the current `0.2.0` so history is continuous.
+4. **Release pipeline** (`.github/workflows/release.yml` + `.goreleaser.yml`):
+   on `push: tags: ["v*"]`, GoReleaser v2 cross-compiles `cmd/envc` for
+   linux/darwin/windows × amd64/arm64 (no windows/arm64), stamps
+   `-X main.version={{.Version}} -X main.commit={{.Commit}} -X main.date={{.Date}}`
+   into the binary, produces `tar.gz` / `zip` archives plus `checksums.txt`,
+   and attaches them to a GitHub Release whose body is generated from commit
+   groups (`feat`, `fix`, `perf`, …).
+5. **No version literals in Go code.** `cmd/envc/main.go` defines
+   `var version = "dev"` (and `commit`, `date`), overridable only at link time.
+   `envc version` prints whatever the release build injected; local
+   `go install` builds report `dev`.
+6. **Dependency hygiene** (`.github/dependabot.yml`): weekly `gomod` and
+   `github-actions` updates, grouped for minor/patch, with conventional
+   `chore(deps)` / `ci(actions)` commit prefixes so release-please classifies
+   them correctly.
+
+## Consequences
+
+- Contributors must use Conventional Commits; otherwise release-please will not
+  bump the version. `chore:` / `docs:` / `ci:` commits produce no release.
+- Breaking changes require `feat!:` or a `BREAKING CHANGE:` footer, which
+  release-please maps to a major bump (subject to `bump-minor-pre-major: true`
+  while the module is pre-1.0).
+- Re-tagging a release manually is discouraged — the tag is the contract that
+  triggers GoReleaser.
+- Codecov token (`CODECOV_TOKEN`) and branch protection enforcing the Tests
+  and Lint checks must be configured in the GitHub repository settings
+  (operational, not code).
+
+## Status
+
+Accepted — 2026-05-02.
+
+## References
+
+- [release-please-action](https://github.com/googleapis/release-please-action)
+- [GoReleaser v2 docs](https://goreleaser.com/customization/)
+- [Conventional Commits 1.0.0](https://www.conventionalcommits.org/en/v1.0.0/)

docs/asr/README.md

@@ -12,3 +12,4 @@ Repo-local decisions for `go-config` (numbering starts at ASR-0001). Org-wide po
 | [ASR-0006](ASR-0006-third-party-library-choices.md) | Third-party library choices |
 | [ASR-0007](ASR-0007-cli-envc-convert-get-merge.md) | CLI `envc`: convert, get, merge |
 | [ASR-0008](ASR-0008-github-presentation-and-release-flow.md) | GitHub presentation and release flow |
+| [ASR-0009](ASR-0009-ci-cd-and-automated-semver.md) | CI/CD pipeline and automated semantic versioning |