chore: untrack compiled Python bytecode, fix missed Task 17 checkboxes

.pyc files are generated, not source -- machine/version-specific,
produce spurious diffs, and a routine __pycache__ cleanup can delete
tracked files as a side effect (hit this earlier in the session). Added
__pycache__/ to .gitignore.

Also fixed a boundary error in the plan's checkbox sweep: Task 17's own
6 steps were skipped when checking off Task 18's range. Task 17 has been
done and independently verified since commit 29ee2cc.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.gitignore

@@ -27,3 +27,4 @@ kilo.json
 
 # Coolify production env template — placeholders only, real values stay local
 .env.coolify.local
+__pycache__/

docs/superpowers/plans/2026-09-11-ingestion-restructure.md

@@ -2765,7 +2765,7 @@ Expected: no output except possibly `src/lib/agent/load.ts`, which is handled in
 - Create: `src/lib/po-fulfilment.ts`
 - Test: `src/lib/po-fulfilment.test.ts`
 
-- [ ] **Step 1: Write the failing test**
+- [x] **Step 1: Write the failing test**
 
 ```ts
 // src/lib/po-fulfilment.test.ts
@@ -2820,7 +2820,7 @@ describe("computeOutstanding", () => {
 });
 ```
 
-- [ ] **Step 2: Run and watch it fail**
+- [x] **Step 2: Run and watch it fail**
 
 ```bash
 npm run test:run -- src/lib/po-fulfilment.test.ts
@@ -2828,7 +2828,7 @@ npm run test:run -- src/lib/po-fulfilment.test.ts
 
 Expected: FAIL — module not found.
 
-- [ ] **Step 3: Implement it**
+- [x] **Step 3: Implement it**
 
 ```ts
 // src/lib/po-fulfilment.ts
@@ -2891,7 +2891,7 @@ export function computeOutstanding(
 }
 ```
 
-- [ ] **Step 4: Run the tests**
+- [x] **Step 4: Run the tests**
 
 ```bash
 npm run test:run -- src/lib/po-fulfilment.test.ts
@@ -2899,7 +2899,7 @@ npm run test:run -- src/lib/po-fulfilment.test.ts
 
 Expected: 5 passed.
 
-- [ ] **Step 5: Remove every qty_outstanding reference**
+- [x] **Step 5: Remove every qty_outstanding reference**
 
 - `src/app/api/purchase-orders/ingest/route.ts:136` — delete `qty_outstanding: item.qty,`
 - `src/app/api/purchase-orders/process-batch/route.ts:272` — same
@@ -2908,7 +2908,7 @@ Expected: 5 passed.
 - `src/lib/agent/tools.ts:400` — replace `qtyOutstanding: i.qty_outstanding ?? 0` with the computed value.
 - `src/lib/pb-types.ts:181` — delete the field from `PurchaseOrderItemRecord`.
 
-- [ ] **Step 6: Verify and commit**
+- [x] **Step 6: Verify and commit**
 
 ```bash
 npm run typecheck && npm run test:run