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/help-root.golden

@@ -0,0 +1,40 @@
+exit: 0
+--- stdout
+idx-cli is a Rust command-line tool for Indonesian stock market (IDX) analysis.
+It supports quote lookup, historical data, local caching, and output formats for both humans and AI agents.
+
+Usage: idx [OPTIONS] <COMMAND>
+
+Commands:
+  stocks       Stock data and analysis
+  config       Manage configuration
+  cache        Manage local cache
+  ownership    Ownership intelligence (bootstrap with `ownership sync`)
+  completions  Generate shell completions
+  version      Show idx-cli version
+  help         Print this message or the help of the given subcommand(s)
+
+Options:
+  -o, --output <OUTPUT>
+          Output format
+          
+          [possible values: table, json]
+
+      --no-color
+          Disable colored output
+
+  -q, --quiet
+          Suppress non-essential output
+
+  -v, --verbose...
+          Increase verbosity (-v, -vv)
+
+      --offline
+          Run without network requests
+
+      --no-cache
+          Bypass local cache
+
+  -h, --help
+          Print help (see a summary with '-h')
+--- stderr