chore: apply plugin version discipline

[intel352]

Part of GoCodeAlone/workflow#760.

Changes:

• keep committed plugin.json.version at the 0.0.0 development sentinel
• remove the obsolete sync-plugin-version workflow when present
• add post-build release validation so the shipped manifest is checked against the tag

Verification:

• wfctl plugin validate-contract .
• wfctl plugin validate-contract --for-publish --tag v9.9.9 .
• GOWORK=off go test ./...

[Copilot]

Pull request overview

Updates the release process to enforce “plugin version discipline”: keep the committed plugin.json at a development sentinel version while ensuring release artifacts ship with a manifest that matches the Git tag.

Changes:

• Set committed plugin.json.version to the 0.0.0 development sentinel.
• Add a post-build release validation step in the release workflow to check the shipped manifest against the tag.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
plugin.json	Keeps the repository-committed manifest version at the 0.0.0 sentinel.
.github/workflows/release.yml	Adds a post-build wfctl plugin validate-contract check intended to validate the shipped manifest against the tag.

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