docs: add design principles to create-expert perstack.toml (#775)

Document the seven design principles established through iterative
refinement of the create-expert pipeline:

1. Built-in Verification (verifier executes, not reviews)
2. Instruction Quality via Binary Checks (subjective checks fail)
3. Domain Agnosticism (not just coding)
4. Plan ↔ write-definition Boundary (plan = raw material)
5. Failure Conditions (hard reject rules, not inverse of success)
6. Instruction Content = Domain Constraints Only
7. Brevity = Focus (verbose dilutes LLM attention)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: FL4TLiN3

definitions/create-expert/perstack.toml

@@ -8,6 +8,66 @@
 #     ├── @create-expert/test-expert      — single query execution (pure executor, no evaluation)
 #     └── @create-expert/verify-test      — artifact inspection + execution + definition review
 # =============================================================================
+#
+# =============================================================================
+# Design Principles
+#
+# 1. Built-in Verification
+#    - Verifier EXECUTES and TESTS artifacts — it is not a code reviewer.
+#    - One verifier per team, not one per executor.
+#    - Verifier must be direct child of coordinator, not nested under executor.
+#    - Verifier needs `exec` in pick list. Without it, verification degrades
+#      to file reading, which cannot catch runtime failures.
+#
+# 2. Instruction Quality via Binary Checks
+#    - Subjective self-checks ("would removing this make output worse?")
+#      do not work — the LLM always judges its own output as necessary.
+#    - Binary checks work: "code block present?" "library name present?"
+#      have unambiguous yes/no answers with clear remediation actions.
+#    - Pattern: structural checks (delegates array, pick list) have always
+#      been followed. Content checks must follow the same binary pattern.
+#
+# 3. Domain Agnosticism
+#    - create-expert must produce experts for ANY domain — coding, writing,
+#      research, design, operations — not just software development.
+#    - Rules and examples in the pipeline must use domain-neutral language.
+#    - Coding-specific vocabulary in rules biases generated experts toward
+#      code-only solutions even when the domain is broader.
+#
+# 4. Plan ↔ write-definition Boundary
+#    - Plan outputs role assignments and domain knowledge, NOT instruction
+#      content. Architecture section = tree structure only (name, one-line
+#      purpose, role). Domain Knowledge section = raw material for
+#      instructions.
+#    - write-definition composes instructions by selecting relevant domain
+#      constraints per expert. It must NOT copy plan details wholesale.
+#    - Without this boundary, plan bloat leaks directly into instructions.
+#
+# 5. Failure Conditions
+#    - Not the inverse of success criteria — they are hard reject rules
+#      derived from deeply understanding the domain.
+#    - Each must specify: what is wrong, which expert caused it, and
+#      where to restart.
+#    - These go into the verifier's instruction so it knows what to reject.
+#
+# 6. Instruction Content = Domain Constraints Only
+#    - An instruction should contain ONLY what the LLM cannot derive on
+#      its own: business rules, quality bars, domain-specific anti-patterns,
+#      completion criteria, priority rules.
+#    - Everything else — implementation techniques, library choices, file
+#      structures, well-known algorithms — is noise that dilutes the signal.
+#    - Enforced by a 6-item binary checklist (no code blocks, no library
+#      names, no file paths, no procedures, no technique explanations,
+#      ≤15 lines for non-coordinator experts).
+#
+# 7. Brevity = Focus
+#    - Verbose instructions dilute LLM attention. The more you write, the
+#      less each sentence weighs. Short, dense instructions outperform
+#      long, thorough ones because the LLM concentrates on what matters.
+#    - This applies at every level: plan.md, instruction fields, and this
+#      pipeline's own definitions. If it can be said in fewer words, it
+#      should be.
+# =============================================================================
 
 # =============================================================================
 # create-expert — Coordinator