Phase 4 of docs/DESIGN.md. Eleven grouped tools (quotes, history, screen,
company, analysis, compare, shareholders, investor holdings, search,
ownership changes, status); ownership_sync is listed only with
--allow-sync. Live results keep the Fetched envelope, errors use the CLI's
{error, code, message} body, and investor tools on an empty database
point at the sync path.
idx-core gains Period/Interval FromStr, Investor::status, a ticker
filter on changes, and Display for ErrorCode (now used by the CLI too).
CLI output and goldens are unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
