feat: foreign flow (idx stocks flow, get_foreign_flow)

`idx stocks flow SYMBOL` shows what foreign investors bought and sold of a
stock, session by session, from IDX's own daily trading summary: foreign
buy, sell and net volume, net value at the session's average price, and
the share of value traded outside the regular board, with range totals.
Latest 10 sessions by default (--days, at most 60) or --from/--to. The MCP
server exposes it as get_foreign_flow.

- api/idx: pure parser for GetStockSummary (rows dated another session
  are dropped) and a provider over curl-impersonate's profile fallback
  with a 30 s limit; Cloudflare passes only some fingerprints.
- flow: each session is cached whole by date, so other stocks' flows for
  the same sessions need no request. Weekends are never requested.
- Idx::idx_code is shared by broker and flow for the .JK-only check.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V3syn2fN2LNo5pvTSqc6eh

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

@@ -68,6 +68,7 @@ Commands:
   fundamental  Run full fundamental analysis on a stock
   broker       Which brokers bought and sold a stock
   bandar       Bandarmology: is buying more concentrated than selling
+  flow         Foreign buying and selling of a stock, session by session
   profile      Get company profile
   financials   Get financial statements
   earnings     Get earnings report
@@ -429,6 +430,57 @@ Examples:
   idx stocks screen --filter high-volume | jq -r '.[].symbol' | idx stocks bandar -
 ```
 
+### `idx stocks flow`
+
+```text
+Foreign buying and selling of a stock, session by session, from IDX's daily trading summary: foreign buy, sell and net volume, the net value at the session's average price, and the share of value traded outside the regular board. End of day. Each session is one request to idx.co.id, which needs curl-impersonate.
+
+Usage: idx stocks flow [OPTIONS] <SYMBOL>
+
+Arguments:
+  <SYMBOL>
+          Single ticker symbol (e.g. BBCA)
+
+Options:
+      --days <DAYS>
+          Latest sessions to show (default 10, at most 60)
+
+  -o, --output <OUTPUT>
+          Output format [default: auto = table on a terminal, json when piped]
+
+          [possible values: auto, table, json, jsonl]
+
+      --from <FROM>
+          First session of a range, YYYY-MM-DD (at most 92 days)
+
+      --no-color
+          Disable colored output
+
+  -q, --quiet
+          Suppress non-essential output
+
+      --to <TO>
+          Last session of the range, YYYY-MM-DD. Default: today
+
+  -v, --verbose...
+          Increase verbosity (-v, -vv)
+
+      --offline
+          Run without network requests
+
+      --no-cache
+          Bypass local cache
+
+  -h, --help
+          Print help (see a summary with '-h')
+
+Examples:
+  idx stocks flow BBCA
+  idx stocks flow BBCA --days 20
+  idx stocks flow BBCA --from 2026-10-01 --to 2026-10-16
+  idx -o json stocks flow BBCA | jq '.foreign_net'
+```
+
 ### `idx stocks profile`
 
 ```text