fix: restore smoke-test workspace changelog for prepare-release

[c-vigo]

Description

Smoke-test RC deploy left workspace CHANGELOG.md as the empty scaffold after init-workspace.sh --smoke-test, so downstream prepare-release.yml failed validation (Unreleased section has no entries). This change copies .devcontainer/CHANGELOG.md to the workspace root during smoke-test install, runs new prepare-changelog unprepare to rename the top ## [semver] - … heading to ## Unreleased, and drops the redundant remap block from the smoke-test dispatch workflow.

Type of Change

• feat -- New feature
• fix -- Bug fix
• docs -- Documentation only
• chore -- Maintenance task (deps, config, etc.)
• refactor -- Code restructuring (no behavior change)
• test -- Adding or updating tests
• ci -- CI/CD pipeline changes
• build -- Build system or dependency changes
• revert -- Reverts a previous commit
• style -- Code style (formatting, whitespace)

Modifiers

• Breaking change (!) -- This change breaks backward compatibility

Changes Made

• packages/vig-utils/src/vig_utils/prepare_changelog.py — Add unprepare_changelog() and prepare-changelog unprepare CLI subcommand (rename first top-level ## [semver] - … to ## Unreleased).
• packages/vig-utils/tests/test_prepare_changelog.py — Unit tests, command-handler tests, main() and subprocess coverage for unprepare.
• assets/init-workspace.sh — After smoke-test rsyncs, copy .devcontainer/CHANGELOG.md → CHANGELOG.md and run prepare-changelog unprepare (requires prepare-changelog on PATH in the install image).
• assets/smoke-test/.github/workflows/repository-dispatch.yml — Remove inline awk/sed remap; keep existence/readability checks for changelogs.
• CHANGELOG.md / assets/workspace/.devcontainer/CHANGELOG.md — Document the fix under the active release section.
• packages/vig-utils/README.md — Document unprepare in the CLI list and examples.

Diff vs release/0.3.1: 7 files, +234 / −11 lines.

Changelog Entry

Paste from ## [0.3.1] - TBD → ### Fixed:

Fixed

• Smoke-test deploy restores workspace CHANGELOG for prepare-release (#417)
  • Add prepare-changelog unprepare to rename the top ## [semver] - … heading to ## Unreleased
  • init-workspace.sh --smoke-test copies .devcontainer/CHANGELOG.md into workspace CHANGELOG.md and runs unprepare; remove duplicate remap from smoke-test dispatch workflow

Testing

• Tests pass locally (just test)
• Manual testing performed (describe below)

Manual Testing Details

N/A (not run in a full smoke-test dispatch; verify with next RC after promoting templates).

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly (edit docs/templates/, then run just docs)
• I have updated CHANGELOG.md under the active ## [0.3.1] - TBD section (and pasted the entry above)
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

Additional Notes

Target base branch: release/0.3.1. After merge, promote updated smoke-test templates / tag an RC so vig-os/devcontainer-smoke-test picks up the fix.

Refs: #417

[Copilot]

Pull request overview

Fixes smoke-test RC deploys leaving the workspace root CHANGELOG.md in an invalid scaffold state that causes downstream prepare-release.yml validation to fail, by normalizing the changelog during smoke-test installs and adding a dedicated prepare-changelog unprepare helper in vig-utils.

Changes:

• Add unprepare_changelog() + prepare-changelog unprepare subcommand to rename the first ## [X.Y.Z] - … heading to ## Unreleased, with unit + CLI/subprocess tests.
• Update init-workspace.sh --smoke-test to copy .devcontainer/CHANGELOG.md to the workspace root and run prepare-changelog unprepare.
• Remove the redundant changelog remap block from the smoke-test dispatch workflow and adjust BATS coverage accordingly; document the fix in both changelog copies and vig-utils README.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/bats/just.bats	Updates BATS assertion to reflect simplified smoke-test changelog checks (remap logic removed from workflow).
packages/vig-utils/tests/test_prepare_changelog.py	Adds comprehensive coverage for unprepare (unit, handler, main(), and subprocess e2e).
packages/vig-utils/src/vig_utils/prepare_changelog.py	Introduces unprepare_changelog() and wires unprepare into the CLI.
packages/vig-utils/README.md	Documents the new prepare-changelog unprepare command in usage and examples.
CHANGELOG.md	Adds release-note entry describing the smoke-test changelog restoration fix.
assets/workspace/.devcontainer/CHANGELOG.md	Mirrors the same release-note entry in the workspace template changelog copy.
assets/smoke-test/.github/workflows/repository-dispatch.yml	Removes inline awk/sed changelog remap now handled during smoke-test install; keeps existence/readability checks.
assets/init-workspace.sh	Implements smoke-test-time changelog copy + prepare-changelog unprepare normalization.

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