P1-FEATURE-011: Optimization Report — Graph Change Verbose Output

Summary

Implement a detailed optimization report that shows node-level changes made by the graph optimizer — before/after diff, per-capability breakdown, and graph size reduction statistics.

Context

Users and developers need detailed visibility into what the graph optimizer changed. This complements the build report (#P1-FEATURE-010) with a deep-dive into optimization decisions.

From plans/release/0501_release_plan/P0_CHECKLIST.md (P1-FEATURE-011).

Current State

• Graph optimizer applies transformations but doesn't generate a change log
• Users can't tell which optimization pass changed what
• Related: #312 (verbose log for graph optimizer), #311 (metadata for rewrite results)

Desired State

• artifacts/optimization_report.json generated after each wmk build run
• Content:
  • Per-pass summary: pass name, nodes removed/added/modified
  • Node-level diff: before/after for each changed node
  • Graph size reduction: node count delta, model size delta (MB)
  • Per-capability breakdown: which optimizations were applied/skipped

Acceptance Criteria

• artifacts/optimization_report.json generated on every wmk build run
• Per-pass record: pass name, nodes removed/added/modified count
• Node-level changes: for each modified node, record op type + change type (fused/removed/rewritten)
• Graph size reduction statistics: total node delta, size delta
• --verbose flag: show full per-node diff in console output
• All existing tests pass

Technical Notes

• Collect change events during each optimizer pass (observer pattern or pass return value)
• Follow-up on #312 and #311 — this issue is the unified report implementation
• Report schema must be stable (will be public API)

Related Files

• plans/release/0501_release_plan/feature-scale.md — P1.11 Optimization Report
• plans/release/0501_release_plan/P0_CHECKLIST.md — P1-FEATURE-011
• #312 — verbose log feature request
• #311 — metadata for rewrite results
• #313 — keep op metadata after fusion