docs: update performance.md with comprehensive multi-project analysis

Expands from 2-project analysis to full 9-project ecosystem-ci coverage
(73 trace files). Adds cross-project comparison table, per-command
breakdown for frm-stack, config loading pattern analysis, and first-run
vs cache-run statistics.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: branchseer