first pass at the newspaper builder

.aidlc/knowledge/aidlc-shared/brownfield.md

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+# Brownfield Safeguards
+
+For any stage that modifies existing code or infrastructure, these safeguards apply.
+
+## Safeguard Matrix
+
+| Safeguard | What It Does | When Applied |
+|-----------|-------------|--------------|
+| **Blast Radius Analysis** | Identifies affected files/components and their downstream dependents | Before code generation (stage `code-generation`, 3.5) |
+| **Diff Preview** | Shows exact proposed changes before applying | Before any file modification |
+| **Test Baseline** | Runs existing tests BEFORE changes to establish baseline | Before code generation (stage `code-generation`, 3.5) |
+| **Test Validation** | Runs existing tests AFTER changes to confirm nothing broke | After code generation (stage `build-and-test`, 3.6) |
+| **Impact Analysis** | Documents affected APIs, components, and dependencies | During reverse engineering (stage `reverse-engineering`, 2.1) and code generation (3.5) |
+| **Rollback Plan** | Documents how to undo changes if needed | Before deployment (stage `deployment-execution`, 4.3) |
+
+## Blast Radius Analysis Template
+
+Before modifying existing code:
+1. List all files that will be changed
+2. For each file, identify: imports/consumers, test files, configuration references
+3. Classify impact: low (isolated change), medium (affects 2-3 dependents), high (cross-cutting)
+4. Present impact summary to user before proceeding
+
+## Test Baseline Protocol
+
+1. Run full test suite before ANY code changes
+2. Record: total tests, passing, failing, skipped, coverage %
+3. After code generation, re-run full test suite
+4. Compare: new failures = regressions introduced by changes
+5. If regressions found, fix before proceeding