test: add golden output parity gate and live A/B compare

Phase 0 of docs/DESIGN.md, before any refactor code:

- tests/golden.rs runs every case in tests/golden/cases.toml (126
  outputs across help, completions, config, cache, all stocks commands
  on MSN and Yahoo mocks, error paths, and ownership queries on a seeded
  fixture DB) and compares exit code, stdout, and stderr byte for byte.
  Regenerate only with UPDATE_GOLDEN=1 for a reviewed output change.
- scripts/live-smoke.sh --compare <old-idx> runs each live case with
  both binaries and fails on differing exit codes, added/missing/retyped
  JSON keys, or changed values for slow-moving data.
- Exclude golden files from the whitespace/EOF pre-commit fixers, which
  would otherwise rewrite pinned help output.

Both gates were fault-injected: a one-word table change fails exactly
the three history goldens, and a binary dropping profile.long_name fails
only the profile live comparison.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/golden/stocks-financials-income.json.golden

@@ -0,0 +1,21 @@
+exit: 0
+--- stdout
+{
+  "instrument": {
+    "id": "bn91jc",
+    "symbol": "BBCA.JK",
+    "name": "Bank Central Asia Tbk PT"
+  },
+  "balance_sheet": null,
+  "cash_flow": null,
+  "income_statement": {
+    "values": {
+      "netIncome": 400000000.0,
+      "totalRevenue": 1000000000.0
+    },
+    "currency": "IDR",
+    "report_date": "2025-12-31",
+    "end_date": "2025-12-31"
+  }
+}
+--- stderr