Add release notes and upgrade guidance for v0.3.0

docs/releases/v0.3.0.md

@@ -0,0 +1,114 @@
+# ReleaseKit v0.3.0
+
+## Summary
+
+ReleaseKit reduces repeated Git processes, validation memory retention, artifact
+hashing, output copying, and runtime metadata parsing. It also improves
+cancellation during validation shutdown and documents module-selected CLI
+adoption and checksum recovery.
+
+## Changes
+
+- Committed-file checks share one lazy Git batch reader per validation operation.
+  Metadata-only checks start no content reader. Cancellation remains active
+  through reader shutdown, and cleanup reaps the child before validation returns.
+- Validation releases regular-file source bytes after inspection and reuses
+  compact or parsed results by blob identity for Go formatting, module
+  replacements, Markdown documents, and symlink targets. Findings retain each
+  source path's locations and destination context.
+- Managed and prebuilt delivery use one local asset verification pass before
+  hosted requests, removing the adjacent declaration-time hashing pass. Changed
+  assets still fail verification; exact remote comparisons, additive retries,
+  and partial-delivery reporting retain their behavior.
+- Go commands transfer completed output buffers without an additional full
+  copy. Status-only successes release their captures, while failures retain
+  complete diagnostics and underlying causes. Capture remains in memory;
+  allocation costs depend on output size and write chunking.
+- The runtime version accessor caches its build-metadata fallback safely across
+  calls. Linker-injected versions retain precedence, and the development fallback
+  remains unchanged.
+- Shutdown errors are attributed to the last validation check that actually read
+  content. Selecting a later check with no applicable files preserves that
+  attribution, and an earlier check failure remains the primary error.
+- CLI-only consumers have documented adoption through versioned Go tool
+  dependencies. The Woodpecker template supports both tool dependencies and
+  ordinary package dependencies selected by the tagged consumer module.
+- Synthetic-module workflow tests use isolated module caches. New checksum
+  investigation guidance explains how to distinguish stale local metadata from
+  a download failure while preserving checksum verification and published tags.
+
+Performance gains depend on the consumer's workload. The changes preserve
+complete in-memory diagnostics and existing validation selections.
+
+## Compatibility
+
+The declared minimum Go version remains 1.25.0, and module dependencies are
+unchanged from v0.2.0. ReleaseKit's maintainer build toolchain and maintained
+Woodpecker template images use Go 1.26.8; consumers select a local toolchain
+compatible with their module and the selected ReleaseKit version.
+
+The root orchestration facade, separate lightweight `buildinfo` facade, public
+signatures, CLI commands, and profile schema are unchanged. Existing v0.2.0
+callers and profiles require no source or configuration migration.
+
+Validation cleanup may now return the caller's cancellation cause where shutdown
+previously remained blocked. Cleanup failures identify the check that used the
+reader. Inspect structured validation errors with `errors.As` and underlying
+causes with `errors.Is`.
+
+Source publication and hosted delivery retain their separate completion states.
+ReleaseKit's deliverables remain the source tag and hosted Gitea note page.
+
+## Upgrade guidance
+
+1. Select v0.3.0 using the dependency form appropriate to the consumer.
+
+   Go API consumers:
+
+   ```sh
+   go get gitea.maximumdirect.net/eric/ReleaseKit@v0.3.0
+   go mod tidy
+   ```
+
+   Consumers using ReleaseKit for repository release commands can register or
+   upgrade the CLI as a Go tool dependency:
+
+   ```sh
+   go get -tool gitea.maximumdirect.net/eric/ReleaseKit/cmd/releasekit@v0.3.0
+   go mod tidy
+   go tool releasekit version
+   ```
+
+   Review and commit the resulting module changes. API and tool dependencies
+   share the consumer's module graph and selected ReleaseKit version.
+
+   A separately installed executable can be updated with:
+
+   ```sh
+   go install gitea.maximumdirect.net/eric/ReleaseKit/cmd/releasekit@v0.3.0
+   ```
+
+2. Retain existing validation and delivery selections. The performance changes
+   apply automatically. Prepare dependencies before offline checks or builds,
+   and run the consumer's ordinary tests after upgrading.
+
+3. For module-selected Woodpecker delivery, commit the dependency upgrade before
+   tagging the consumer. Choose a compatible local Go image; delivery and retries
+   continue to use the triggering tag's module selection. CLI-only consumers can
+   use the tool declaration to retain ReleaseKit through `go mod tidy`.
+
+4. If dependency preparation reports a checksum mismatch, follow the
+   [checksum investigation guide](https://gitea.maximumdirect.net/eric/ReleaseKit/src/tag/v0.3.0/docs/consumers/delivery.md#investigating-module-checksum-mismatches).
+   Repair a confirmed stale cache entry while retaining checksum verification
+   and the application's recorded checksums.
+
+See the
+[adoption guide](https://gitea.maximumdirect.net/eric/ReleaseKit/src/tag/v0.3.0/docs/consumers/adoption.md),
+[candidate check guide](https://gitea.maximumdirect.net/eric/ReleaseKit/src/tag/v0.3.0/docs/consumers/check.md),
+[delivery guide](https://gitea.maximumdirect.net/eric/ReleaseKit/src/tag/v0.3.0/docs/consumers/delivery.md),
+and [runtime version guide](https://gitea.maximumdirect.net/eric/ReleaseKit/src/tag/v0.3.0/docs/consumers/runtime-version.md)
+for supported behavior and usage.
+
+[COPYRIGHT](https://gitea.maximumdirect.net/eric/ReleaseKit/src/tag/v0.3.0/COPYRIGHT) |
+[LICENSE](https://gitea.maximumdirect.net/eric/ReleaseKit/src/tag/v0.3.0/LICENSE) |
+[ATTRIBUTION](https://gitea.maximumdirect.net/eric/ReleaseKit/src/tag/v0.3.0/docs/oss/attribution.md)