feat(mcp): add idx-mcp, a stdio MCP server over idx-core

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>

ROADMAP.md

@@ -15,12 +15,11 @@ history lives in git.
 ## Workflow
 - `watchlist`: named symbol sets usable by other commands
 - `alerts`: price alerts with a daemon
-- CSV/TSV and JSONL output
-- Stdin symbol input for chaining (`... | idx stocks fundamental --stdin`)
+- CSV/TSV output
 - Additional providers (Alpha Vantage, Twelve Data, IDX official)
 
 ## Agent integration
-- MCP server exposing the existing commands as tools (planned as `idx-mcp`)
+- Publish `idx-mcp` (crates.io, npm, release assets); see `docs/DESIGN.md` phase 5
 - JSON Schema export for command output
 - Composite `analyze` command (quote, fundamentals, ownership, sentiment)
 
@@ -29,5 +28,7 @@ history lives in git.
   can still fail.
 - `stocks technical` reports the SMA200 trend as unavailable when fewer than
   200 daily candles are returned.
+- MSN's `low-pe` screen returned no priced stocks on 2026-10-14 (upstream;
+  other filters work).
 - MSN history for IDX is price-only (`1mo`, `3mo`, `1y`); Yahoo stays the
   default OHLCV source.