systematic-debugging

# Execute Bug, failure, or unexpected behavior: 1. **Isolate** — read error, reproduce, inspect the diff, and drill upward through diagnostic layers: L1 symptom → L2 logic → L3 system → L4 architecture → L5 cross-system contract → L6 platform → L7 spec gap. Layers are observation altitudes, not one causal chain; the causal shape at the stop altitude is classified explicitly before any root claim. Stop only when causal proof accounts for the recurrence generator or reaches a T-class boundary. 2. **Identify owner** — compare working behavior, trace the bad value, locate the canonical owner, and treat duplicate owners as a finding. 3. **Decide before editing** — Before fixing, run Patch-Shape Triage and Ripple Signal Triage when shared logic, contracts, fallbacks, adapters, producer/consumer seams, or source-of-truth boundaries are involved. Surface Change Necessity for any new source-code path or non-trivial source edit. Run Minimality Check for a new branch, fallback, adapter, owner, or compatibility path, and Pre-Edit Complexity Check for an overloaded owner or complexity growth. After Change Necessity selects `code-change` and before the first repair edit, own the TDD Route for the repair slice: `off` skips automatic TDD; `auto` selects `strict` on any behavior, bugfix, shared/core, contract, persistence, permission, migration, producer/consumer, or meaningful regression signal. `light` requires every tiny/low-risk/single-own...