Initial commit: pygenium as git submodule

tasks/11-check-defensive-guards.md

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+# 11. Redundant defensive guarding check
+
+meta:
+  id: pygienium-11
+  feature: pygienium
+  priority: P2
+  depends_on: [pygienium-06]
+  tags: [check]
+
+objective:
+
+- Implement the redundant-defensive-guarding check: remove excessive null checks, unnecessary try/catch, fallback paths that mask bugs, defensive code guarding invariants the type system already guarantees.
+
+deliverables:
+
+- `src/checks/defensive-guards.ts`: `CheckDefinition` with scan + fix tasks
+- Rubric: redundant null/undefined checks where types are non-nullable, try/catch that only rethrows or swallows, fallback values that hide errors, defensive guards on already-validated input, compatibility fallbacks (engineering rule: remove, don't layer)
+- `/pygienium-defensive-guards` runs E2E
+
+steps:
+
+- Author `buildScanTask`: agent identifies defensive smells, writes `pygienium/checks/defensive-guards/findings.md`
+- Author `buildFixTask`: remove redundant guards; preserve guards that protect real external boundaries (user input, IO, parsing); write changes.md distinguishing removed vs kept-with-reason
+- Register the check
+
+tests:
+
+- Integration: temp file with a null check on a typed-non-null param + a try/catch that swallows; run `--fix`; assert removed; assert a JSON.parse guard is preserved
+
+acceptance_criteria:
+
+- findings.md separates redundant guards from legitimate boundary guards
+- `--fix` removes redundant guards and keeps boundary guards (IO, parsing, untrusted input)
+
+validation:
+
+- Inspect `pygienium/checks/defensive-guards/{findings.md,changes.md}`
+
+notes:
+
+- Key judgment: guarding external boundaries (IO, untrusted input, parsing) is correct; guarding internal invariants the type system guarantees is noise
+- Engineering rule: no compatibility layers or fallbacks meant to be replaced later