chore: centralize versioning and release-please automation for v0.9.2

[EndersonPro]

Summary

• Introduce a single source of truth for releases using the root VERSION file set to 0.9.2.
• Add release-please automation (release-please-config.json, .release-please-manifest.json, and workflow) to drive tag/release flow from merges to main.
• Enforce version consistency in CI and release packaging via version contract checks and CLI version injection/verification.

Validation

• ./scripts/check_version_contract.sh
• ARCH=arm64 ./scripts/package_macos.sh contract
• go test ./...