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-screen-worst.json.golden

@@ -0,0 +1,35 @@
+exit: 0
+--- stdout
+[
+  {
+    "symbol": "BBCA.JK",
+    "price": 9875,
+    "change": 117,
+    "change_pct": 1.2,
+    "volume": 12300000,
+    "market_cap": 1215200000000000,
+    "week52_high": 10500,
+    "week52_low": 8000,
+    "week52_position": 0.75,
+    "range_signal": "upper",
+    "prev_close": 9758,
+    "avg_volume": 10000000,
+    "as_of": null
+  },
+  {
+    "symbol": "BBRI.JK",
+    "price": 5100,
+    "change": 210,
+    "change_pct": 4.3,
+    "volume": 22200000,
+    "market_cap": 780000000000000,
+    "week52_high": 5400,
+    "week52_low": 3900,
+    "week52_position": 0.8,
+    "range_signal": "upper",
+    "prev_close": 4890,
+    "avg_volume": 18000000,
+    "as_of": null
+  }
+]
+--- stderr