feat: add autoresearch-style experiment loop for canonicalization tuning
Externalize 35 hardcoded thresholds into src/experiment-config.ts so an
AI agent can autonomously search the parameter space. Includes eval harness
(experiments/eval-runner.ts) with composite scoring, TSV logging, and
agent instruction manual (experiments/program.md).
Baseline score: 0.8785 (recall 100%, typeAcc 94%, coverage 96%, D-rate 66%)