chore(release): enforce Pi package version coherence

[dnlrsls]

📋 Pre-flight Checks

• I have searched existing issues and this is not a duplicate
• I understand this issue needs status:approved before a PR can be opened

🔍 Problem Description

Pi package version 0.1.11 is duplicated in plugin/pi/package.json, plugin/pi/cli.js, and plugin/pi/test/package-contract.test.mjs. The .github/workflows/publish-pi.yml workflow accepts any pi-v* tag without verifying those values agree. Closed issues #579, #488, and #371 handled individual releases or version bumps; issue #791 concerns mise-managed installation, not an automated consistency guard.

💡 Proposed Solution

Establish package metadata as the authoritative version and add tag/package/CLI consistency checks before publication.

Acceptance criteria:

• CLI installation guidance derives from one authoritative package version.
• A pi-vX.Y.Z tag that disagrees with package.json blocks publication.
• Contract tests detect package/CLI version drift.
• The explicit legacy 0.1.8 migration behavior remains unchanged.

Verification: prove matching metadata/tag passes and a deliberate mismatch fails before npm publication.

Non-goals: performing a version bump, redesigning the Pi package, or removing legacy migration behavior.

📦 Affected Area

Other

🔄 Alternatives Considered

Continue synchronizing duplicated versions manually. Rejected because previous version bumps show this is repetitive and error-prone.

📎 Additional Context

Current evidence is in plugin/pi/package.json, plugin/pi/cli.js, plugin/pi/test/package-contract.test.mjs, and .github/workflows/publish-pi.yml.