docs: update build performance benchmarks (3.0.0)

[github-actions]

Automated build benchmark update for 3.0.0 from workflow run #171.

[greptile-apps]

Greptile Summary

Automated benchmark update for v3.0.0 from CI workflow, updating performance metrics in both the main README and detailed benchmark documentation.

Key changes:

• Updated README performance table with v3.0.0 metrics
• Added v3.0.0 entries to historical benchmark comparison table
• Included detailed build phase breakdowns and query latency data
• Updated raw JSON benchmark data for programmatic access

Data consistency verified:

• All metrics between README.md and BUILD-BENCHMARKS.md are consistent
• Percentage changes and trend indicators (↑/↓) are correctly calculated
• File count increased from 146 to 164 files, explaining some performance deltas
• Formatting follows established patterns from previous versions

Confidence Score: 5/5

• This PR is safe to merge with minimal risk - automated documentation update only
• Documentation-only changes from automated CI workflow with no code modifications; all benchmark data is internally consistent between files; formatting follows established patterns; no logical errors or security concerns
• No files require special attention

Important Files Changed

Filename	Overview
README.md	Updated performance benchmarks table with v3.0.0 metrics - all values consistent with detailed benchmark data
generated/benchmarks/BUILD-BENCHMARKS.md	Added comprehensive v3.0.0 benchmark data including historical comparison, phase breakdowns, and raw JSON - all formatting correct

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