feat(cli): agent-native output, stdin symbols, and exit-code classes

Phase 1 of docs/DESIGN.md:

- Output format resolves -o > IDX_OUTPUT > general.output > auto; auto
  is a table on a terminal and JSON when stdout is piped or captured.
  `config init` now writes output = "auto".
- JSON is pretty only on a terminal and compact otherwise. New `-o
  jsonl` prints one array item per line with the same key order.
- No ANSI color when stdout is not a terminal (direct owo-colors calls
  now go through output::style).
- `stocks quote -` and `stocks compare -` read symbols from stdin.
- Exit codes by class: 2 invalid input/config, 3 not found or cache
  miss, 4 upstream unavailable, 5 unsupported, 1 other.

Golden changes are limited to those documented kinds and were verified
mechanically: JSON goldens are semantically identical, tables differ
only by removed ANSI codes and the column padding comfy-table had
reserved for them (cell contents identical), exit codes match each
error's class, and help/completions only gain the new --output values.
17 new golden cases cover auto, jsonl, stdin, and the new errors.

tests/cli.rs now pins IDX_OUTPUT=table in its harness (its tests assert
table text and run piped) and parses discover JSON instead of matching
pretty-printed whitespace.

Live A/B against main: 16/16 stocks cases identical; ownership discover
got IDX 403 on both binaries, now exiting 4 instead of 1 as intended.

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

tests/golden/stocks-fundamental.table.golden

@@ -1,49 +1,49 @@
 exit: 0
 --- stdout
-Fundamental Analysis for BBCA.JK
+Fundamental Analysis for BBCA.JK
 
-Growth Analysis for BBCA.JK
-┌─────────────────┬─────────┬────────────────────┐
-│ METRIC          ┆ VALUE   ┆ SIGNAL             │
-╞═════════════════╪═════════╪════════════════════╡
-│ Revenue Growth  ┆ +8.10%  ┆ slow     │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ Earnings Growth ┆ +12.10% ┆ moderate │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ Overall         ┆ -       ┆ mixed    │
-└─────────────────┴─────────┴────────────────────┘
+Growth Analysis for BBCA.JK
+┌─────────────────┬─────────┬──────────┐
+│ METRIC          ┆ VALUE   ┆ SIGNAL   │
+╞═════════════════╪═════════╪══════════╡
+│ Revenue Growth  ┆ +8.10%  ┆ slow     │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
+│ Earnings Growth ┆ +12.10% ┆ moderate │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
+│ Overall         ┆ -       ┆ mixed    │
+└─────────────────┴─────────┴──────────┘
 
-Valuation Analysis for BBCA.JK
-┌────────────────┬─────────┬─────────────────────┐
-│ METRIC         ┆ VALUE   ┆ SIGNAL              │
-╞════════════════╪═════════╪═════════════════════╡
-│ P/E (Trailing) ┆ 25.40   ┆ premium   │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ P/E (Forward)  ┆ -       ┆ -                   │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ Price/Book     ┆ 4.60    ┆ expensive │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ ROE            ┆ +19.80% ┆ strong    │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ Net Margin     ┆ +32.40% ┆ excellent │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ EV/EBITDA      ┆ -       ┆ no data   │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ Overall        ┆ -       ┆ expensive │
-└────────────────┴─────────┴─────────────────────┘
+Valuation Analysis for BBCA.JK
+┌────────────────┬─────────┬───────────┐
+│ METRIC         ┆ VALUE   ┆ SIGNAL    │
+╞════════════════╪═════════╪═══════════╡
+│ P/E (Trailing) ┆ 25.40   ┆ premium   │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
+│ P/E (Forward)  ┆ -       ┆ -         │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
+│ Price/Book     ┆ 4.60    ┆ expensive │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
+│ ROE            ┆ +19.80% ┆ strong    │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
+│ Net Margin     ┆ +32.40% ┆ excellent │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
+│ EV/EBITDA      ┆ -       ┆ no data   │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
+│ Overall        ┆ -       ┆ expensive │
+└────────────────┴─────────┴───────────┘
 
-Risk Analysis for BBCA.JK
-┌───────────────┬────────┬─────────────────────────┐
-│ METRIC        ┆ VALUE  ┆ SIGNAL                  │
-╞═══════════════╪════════╪═════════════════════════╡
-│ Debt/Equity   ┆ 0.42   ┆ conservative  │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ Current Ratio ┆ 1.18   ┆ tight         │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ ROA           ┆ +3.10% ┆ -                       │
-├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
-│ Overall       ┆ -      ┆ moderate risk │
-└───────────────┴────────┴─────────────────────────┘
+Risk Analysis for BBCA.JK
+┌───────────────┬────────┬───────────────┐
+│ METRIC        ┆ VALUE  ┆ SIGNAL        │
+╞═══════════════╪════════╪═══════════════╡
+│ Debt/Equity   ┆ 0.42   ┆ conservative  │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
+│ Current Ratio ┆ 1.18   ┆ tight         │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
+│ ROA           ┆ +3.10% ┆ -             │
+├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
+│ Overall       ┆ -      ┆ moderate risk │
+└───────────────┴────────┴───────────────┘
 
-Overall Signal: mixed
+Overall Signal: mixed
 --- stderr