Release probbit 0.8.1

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Summary

• Prepare the 0.8.1 patch release after Harden CLI, integrations, browser and processor release contracts #26: align workspace packages, internal dependency requirements, the lockfile and npm metadata.
• Publish the patch changelog and update current-version installation and monitor documentation; retain historical benchmark results.
• Preserve the 0.8.0 strand compatibility golden using its historical engine header, while checking that fresh headers identify the current binary and continued strands verify.

Verification

• Targeted historical-strand compatibility, Node wrapper and installer contract checks.
• Release build and local clean-prefix shell/npm package checks.
• The full cross-platform CI matrix runs on this pull request before merge.

This change prepares release metadata. GitHub release archives and the npm package are published separately after artifact review; no frozen benchmark results are being relabelled as new measurements.