feat: login-free Stockbit intraday and quote provider

Read Stockbit's public symbol page (__NEXT_DATA__) with a plain ureq
request and an honest user agent: `stocks intraday` (today by the
minute, any provider), `--provider stockbit` quotes with the best
bid/offer only while the market is open, and MCP `get_intraday`.

- UPSTREAMBLOCKED error (exit 4) for a CDN 403; never retried
- requests paced 1 s apart across idx processes, 5 s snapshot cache
- global --provider flag (yahoo, msn, stockbit)
- roadmap: L1 ships from Stockbit; depth stays a login follow-on

web/src/content/docs/cli/stockbit.md

@@ -0,0 +1,75 @@
+---
+title: Stockbit
+description: Today's session by the minute and quotes with best bid/offer, from Stockbit's public page. Opt-in, no account.
+---
+
+[Stockbit](https://stockbit.com)'s public symbol page carries a quote, the
+best bid and offer, and today's price for every minute of the session. idx
+reads that page directly. It needs no Stockbit account, no login and no
+helper tools.
+
+```bash
+idx stocks intraday BBCA                     # today's session, by the minute
+idx stocks intraday ^JKSE                    # an index (or IHSG, LQ45)
+idx --provider stockbit stocks quote BBCA    # quote with bid/offer
+idx -o json stocks intraday BBCA | jq '.points | length'
+```
+
+## What you get
+
+| | `stocks intraday` | `--provider stockbit stocks quote` |
+| --- | --- | --- |
+| Price, change, previous close, volume | yes | yes |
+| Best bid and offer | while the market is open | while the market is open |
+| Market status (`market_status`) | yes | yes |
+| Price per minute (`points`) | yes | no |
+| Market cap, 52-week range | no | no |
+
+- **Delayed.** Stockbit's terms describe its market data as "a real-time
+  snapshot, delayed at least 10 minutes". It is not a live feed.
+- **Bid and offer only while trading.** Outside the session, Stockbit still
+  shows the book as it closed. idx leaves `bid` and `offer` out then, so the
+  closing book never passes for a live one.
+- **Top of the book only.** One bid and one offer price, no depth. The full
+  order book needs a Stockbit login, which idx does not do.
+- **Prices only.** The page has no per-minute volume or OHLC.
+- **Empty sessions are data.** A suspended or delisted stock answers with
+  `points: []` and a `session_note` saying so (`Stockbit lists the stock as
+  suspended`). An active stock with no volume says `no trades this session`,
+  even when its chart is a flat line at the previous close. Neither is an
+  error.
+
+`--provider stockbit` (or `IDX_PROVIDER=stockbit`, or
+`idx config set general.provider stockbit`) changes only where quotes come
+from. History still comes from Yahoo. Company data, fundamentals and
+screening answer `UNSUPPORTED` under it, so use MSN for those.
+
+## How idx talks to Stockbit
+
+- One request per symbol to `https://stockbit.com/symbol/<CODE>`, at least one
+  second apart across all your idx processes (a shell loop of `idx` calls
+  included), cached for 5 seconds.
+- An honest user agent, `idx-cli/<version> (+https://github.com/0xrsydn/idx-cli)`,
+  not a browser disguise. Stockbit's CDN refuses some generic agents
+  (`curl/…`) outright but lets this one through. No curl-impersonate
+  needed.
+- No retries. If Stockbit's CDN refuses your machine, the command fails at
+  once with `UPSTREAMBLOCKED` (exit `4`):
+
+  ```json
+  {"error":true,"code":"UPSTREAMBLOCKED","message":"upstream blocked: stockbit.com refused this client (HTTP 403 from its CDN); ..."}
+  ```
+
+  Wait, or try from another network. `--provider msn` serves quotes without
+  Stockbit.
+
+## Terms
+
+Stockbit's [terms](https://stockbit.com/terms) allow its content for personal,
+non-commercial use. They prohibit data mining, robots and redistribution
+without Stockbit's written consent. idx is not affiliated with or endorsed by
+Stockbit. Use this for looking at a stock now and then, not for crawling the
+market or republishing prices.
+
+Over MCP, the same data comes from the `get_intraday` tool, and from
+`get_quotes` when the server runs with `IDX_PROVIDER=stockbit`.