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/ownership-concentration.table.golden

@@ -0,0 +1,14 @@
+exit: 0
+--- stdout
+┌──────┬────────┬────────┬────────┬──────┬─────────────┬─────────┐
+│ RANK ┆ TICKER ┆ TOP1%  ┆ TOP3%  ┆ HHI  ┆ FREE_FLOAT% ┆ HOLDERS │
+╞══════╪════════╪════════╪════════╪══════╪═════════════╪═════════╡
+│ 1    ┆ AALI   ┆ 79.68% ┆ 79.68% ┆ 6348 ┆ 20.32%      ┆ 1       │
+├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
+│ 2    ┆ BBCA   ┆ 54.94% ┆ 57.16% ┆ 3021 ┆ 41.82%      ┆ 4       │
+├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
+│ 3    ┆ AADI   ┆ 41.10% ┆ 62.30% ┆ 2009 ┆ 20.30%      ┆ 10      │
+├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
+│ 4    ┆ ABBA   ┆ 2.83%  ┆ 4.18%  ┆ 9    ┆ 95.82%      ┆ 2       │
+└──────┴────────┴────────┴────────┴──────┴─────────────┴─────────┘
+--- stderr