refactor: adopt Hard Signal Framework for create-expert verification (#781)

* refactor: adopt Hard Signal Framework for create-expert verification pipeline

Replace soft signal verification (LLM judgment) with hard signal verification
(deterministic commands with expected outputs). Key changes:

- Design Principle 1: "Built-in Verification" → "Hard Signal Verification"
  with three conditions: Ground truth, Context separation, Determinism
- Plan: 3 test queries → 1 comprehensive query with deep signal coverage
- Build loop: sequential 3-query cycle → write → test → verify with
  reproducibility confirmation
- Verify-test: artifact inspection + semantic review → hard signal execution
  + reproducibility check + structural checks
- Verdict system: PASS/SUFFICIENT/CONTINUE → PASS/CONTINUE

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: remove coding-specific vocabulary from Hard Signal Framework descriptions

Replace "exit codes, test results, grep matches" and similar coding-centric
examples with domain-neutral language per Design Principle 3 (Domain
Agnosticism). create-expert serves all domains, not just software development.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: FL4TLiN3

.changeset/hard-signal-verification.md

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+"perstack": patch
+---
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+refactor: adopt Hard Signal Framework for create-expert verification pipeline