docs: update build performance benchmarks (3.0.0)

[github-actions]

Automated build benchmark update for 3.0.0 from workflow run #172.

[greptile-apps]

Greptile Summary

Automated benchmark update for v3.0.0 showing measured performance metrics across both files.

• Updated performance table in README.md with latest 3.0.0 metrics
• Added detailed 3.0.0 benchmark entries to BUILD-BENCHMARKS.md with full JSON data
• All calculations and percentage changes are mathematically correct
• Data format and structure consistent with previous benchmark entries

Note: The benchmarks show significant performance regression from 2.6.0 to 3.0.0 (native build speed: 1.9 → 4.5 ms/file, 1-file rebuild: 124ms → 332ms), but this PR is simply documenting the measured data accurately from the automated workflow.

Confidence Score: 5/5

• This PR is safe to merge with no risk
• Automated documentation update with verified calculations and consistent formatting - no code changes or logic modifications
• No files require special attention

Important Files Changed

Filename	Overview
README.md	Updated performance metrics table with 3.0.0 benchmark data - all values match BUILD-BENCHMARKS.md
generated/benchmarks/BUILD-BENCHMARKS.md	Added comprehensive 3.0.0 benchmark entries with raw data, phase breakdowns, and JSON metadata

_{Last reviewed commit: 315edc2}

[greptile-apps]

_{2 files reviewed, no comments}

_{Edit Code Review Agent Settings | Greptile}

[carlos-alm]

Duplicate of #299 — caused by dev-push Publish triggering a second Benchmark run. Fixed in upcoming PR.