feat: corporate actions from the Stockbit session (stocks actions, stocks calendar)

`idx stocks actions SYM [--kind ...]`: one stock's cash and stock
dividends, bonus shares, rights, warrants, splits and reverse splits,
meetings, public exposes and tender offers (`--kind ipo` adds its IPO),
newest first. `idx stocks calendar [--from] [--to] [--kind ...]`: the
market's actions dated in the range (default today and 30 days ahead),
oldest first. MCP: get_corporate_actions, get_corporate_calendar.

Stockbit's `/corpaction/{type}` serves one kind per request; each type has
its own field prefix and list key, so entitlements are read by field
suffix. An action's `date` is the cum date for entitlements, else the
event's first day. Dividends keep their decimals. One request per kind,
cached 6 hours. AUTHERROR without a session.

Fixtures are the 2026-11-03 recordings (market-wide ones trimmed to
October-December). Goldens added; help-stocks and completions-bash gain
the two subcommands, MCP tools.json the two tools (regenerated with
UPDATE_GOLDEN=1). The MCP docs counted 17 tools without stockbit_login;
now 20.

Claude-Session: https://claude.ai/code/session_01RqPPVeVDrnLoP7NUZmLRxY

README.md

@@ -97,7 +97,8 @@ idx ownership changes --from 2026-07-31 --to 2026-08-31
   minute) and `--provider stockbit` quotes with the best bid/offer while the
   market is open, delayed at least 10 minutes. With your own account
   (`idx stockbit login`): `stocks orderbook` depth, live
-  quotes and Stockbit daily history. Personal use under Stockbit's terms; see
+  quotes, Stockbit daily history, and corporate actions (`stocks actions`,
+  `stocks calendar`: dividends, rights, splits, meetings, IPOs and more). Personal use under Stockbit's terms; see
   the [Stockbit page](https://idx.rasyidanaf.com/cli/stockbit/)
 - Local file cache with TTL, and `--offline` mode with stale-cache fallback
 
@@ -165,8 +166,9 @@ change it to `auto` with `idx config set general.output auto`.
 
 ## MCP server
 
-`idx-mcp` serves the same data to MCP clients over stdio, as 17 tools:
-`get_quotes`, `get_intraday`, `get_orderbook`, `stockbit_status`, `get_price_history`, `screen_stocks`, `get_company`,
+`idx-mcp` serves the same data to MCP clients over stdio, as 20 tools:
+`get_quotes`, `get_intraday`, `get_orderbook`, `get_corporate_actions`,
+`get_corporate_calendar`, `stockbit_status`, `stockbit_login`, `get_price_history`, `screen_stocks`, `get_company`,
 `analyze_stock`, `compare_stocks`, `get_broker_summary`, `analyze_bandar`,
 `get_foreign_flow`, `get_shareholders`, `get_investor_holdings`,
 `search_investors`, `get_ownership_changes`, and `ownership_status`. Live results come wrapped as