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-profile.json.golden

@@ -0,0 +1,27 @@
+exit: 0
+--- stdout
+{
+  "id": "feee16af-c94c-465d-a59d-a9727c22bd0e",
+  "symbol": "BBCA",
+  "short_name": "Bank Cntrl Asia",
+  "long_name": "PT Bank Central Asia Tbk",
+  "description": "PT Bank Central Asia Tbk (the Bank) is an Indonesia-based commercial bank.",
+  "sector": "Financials",
+  "industry": "Banking Services",
+  "website": "https://www.bca.co.id/",
+  "employees": 27937,
+  "address": "Menara BCA, Grand, Jl. MH Thamrin No. 1",
+  "city": "JAKARTA PUSAT",
+  "country": "Indonesia",
+  "phone": "+62 21 23588000",
+  "officers": [
+    {
+      "name": "Jahja Setiaatmadja",
+      "title": "President Director",
+      "age": 69,
+      "year_born": 1955,
+      "total_pay": 12000000000
+    }
+  ]
+}
+--- stderr