Add V3 benchmark dashboard and final results

[skyoo2003]

Description

Adds the measured V3 delta-search implementation and preserves its final Redis/Valkey benchmark evidence. The GitHub Pages reference dashboard now shows the final release-gate results alongside the archived V3 baseline and R2/R3 measurements; the obsolete Valkey crash excerpt is removed.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (bug fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Test update

Checklist

• Tests pass (make test)
• Vet/make vet
• Linting passes (make lint)
• Build succeeds (make build)
• Documentation updated if needed
• Changelog fragment added (changes/unreleased/20260913-v3-delta-search.yaml)
• Commit messages follow guidelines

Additional Notes

• make all passed.
• Hugo 0.147.9, the GitHub Pages workflow version, built the site successfully.
• The final delta-search release gate remains failed: Redis had 202/555 and Valkey 208/555 search p95 failures; DeltaSearch remains opt-in.
• The dashboard links the raw JSON results and reports the archived V3/R2-R3 sets separately because they use a different schema.

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By submitting this PR, I agree that my contributions will be licensed under the Apache License 2.0.