test: add macro-generated test batteries for report types

[rocketman-code]

Context

Parent: #160

Five report types (TraceReport, ChainReport, CutReport, DiffReport, PackagesReport) each need the same set of tests: JSON field validation, terminal output format, empty-data handling, large-data handling. Writing these by hand is repetitive and error-prone — exactly the case RFR recommends macro-generated test batteries.

Expected Behavior

A test_battery! macro that generates a standard set of tests for each report type, reducing per-type boilerplate to one line.

Scope

• test_battery! macro that takes a report type and a constructor closure
• Generated tests per type:
  • to_json() produces valid JSON
  • to_json() field names match expected set
  • to_terminal() produces non-empty output
  • to_terminal() with color: false produces no ANSI codes
  • Empty data (zero modules/packages) doesn't panic
  • Round-trip: to_json() contains all data from the struct
• Add one invocation per report type