Harden AI agent rules and compile learning workflow

docs/00-governance/common_failures.md

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+# Common Compile Failures
+**Last Updated:** 2026-04-05
+
+Record concise error fingerprints and verified fixes.
+
+## Entry Template
+- **Date:** YYYY-MM-DD
+- **Error:** `CSXXXX`
+- **Fingerprint:** file + line + short symptom
+- **Root cause:** one sentence
+- **Fix:** one to three concrete steps
+- **Prevention link:** guardrail/pattern doc entry added
+
+## Starter Examples
+1. **`CS0115` no suitable method found to override**
+   - Root cause: incorrect NT8 override signature.
+   - Fix: replace with exact official signature; recompile.
+
+2. **`CS0507` cannot change access modifiers when overriding**
+   - Root cause: used `public override`/`private override` instead of `protected override`.
+   - Fix: change to `protected override`; recompile.
+
+3. **`CS0246` type or namespace not found**
+   - Root cause: missing using/namespace or undefined domain type.
+   - Fix: add correct namespace reference or confirmed type definition.
+
+4. **`CS1503` argument type mismatch**
+   - Root cause: wrong overload or argument ordering.
+   - Fix: align call with exact method signature and parameter types.
+
+5. **C# 6+ syntax in C# 5 project**
+   - Root cause: use of `$""`, `?.`, `nameof`, expression-bodied members, etc.
+   - Fix: rewrite using C# 5 compatible constructs.

docs/00-governance/compile_guardrails.md

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+# Compile Guardrails
+**Last Updated:** 2026-04-05
+
+Preventive rules to reduce repeat compile failures.
+
+## Core Prevention Rules
+- [ ] Verify NT8 signatures in official docs before adding/changing any `protected override`.
+- [ ] Keep NinjaScript edits within task scope and allowed file boundaries.
+- [ ] Enforce C# 5.0 syntax only; reject C# 6+ constructs.
+- [ ] Keep managed order sequence correct (stop/target before entry on same bar).
+- [ ] Guard `OnBarUpdate` by `BarsInProgress` and bar readiness.
+- [ ] Do not use unsupported attributes/types/enums without confirmation.
+
+## Verification Gates
+- [ ] Run `.\verify-build.bat` after changes.
+- [ ] Run focused tests for changed area.
+- [ ] If NinjaScript touched, compile in NT8 NinjaScript Editor.
+
+## Update Rule
+- [ ] Add a new guardrail entry whenever a compile issue reveals a missing prevention rule.

docs/00-governance/patterns_and_antipatterns.md

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+# Patterns and Anti-Patterns
+**Last Updated:** 2026-04-05
+
+Capture recurring implementation patterns that impact compile stability.
+
+## Pattern Entry Template
+- **Context:** where this applies
+- **Good pattern:** concise example/description
+- **Anti-pattern:** concise example/description
+- **Why it matters:** one sentence
+
+## Starter Patterns
+1. **NT8 override signatures**
+   - Good pattern: copy exact signature from official NT8 docs before coding.
+   - Anti-pattern: infer or copy from outdated examples.
+   - Why it matters: prevents `CS0115` and runtime integration drift.
+
+2. **Access modifier on overrides**
+   - Good pattern: use `protected override` for NT8 lifecycle/event methods.
+   - Anti-pattern: `public override` or `private override`.
+   - Why it matters: prevents `CS0507`.
+
+3. **C# 5 compatibility discipline**
+   - Good pattern: `string.Format`, explicit null checks, block-bodied members.
+   - Anti-pattern: string interpolation, null-conditional, expression-bodied members.
+   - Why it matters: prevents avoidable language-version compile failures.
+
+4. **Managed order sequencing**
+   - Good pattern: set stop/target before entry on the same bar.
+   - Anti-pattern: entry first, then stop/target.
+   - Why it matters: avoids silent behavior defects and rejected assumptions.
+
+5. **Scope-first fixes**
+   - Good pattern: smallest safe change in scoped files only.
+   - Anti-pattern: broad cleanup or adjacent-file edits during bugfix.
+   - Why it matters: reduces regression risk and review churn.