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

scripts/live-smoke.sh

@@ -123,6 +123,12 @@ contract() {
             echo '(.highlights | type == "array") and (.risks | type == "array")' ;;
         "stocks news "*)
             echo 'type == "array" and all(.[]; (.title | type == "string") and (.url | type == "string"))' ;;
+        "stocks broker "*)
+            echo '(.symbol | type == "string") and (.buyers | length > 0) and (.sellers | length > 0) and all(.buyers[]; (.code | type == "string") and (.value | type == "number")) and (.total_value | type == "number")' ;;
+        "stocks bandar "*)
+            echo 'type == "array" and length > 0 and all(.[]; (.method | type == "string") and (.tiers | length == 4) and (.imbalance_bps | type == "number"))' ;;
+        "stocks flow "*)
+            echo '(.days | length > 0) and all(.days[]; (.date | type == "string") and (.foreign_buy | type == "number") and (.foreign_sell | type == "number")) and (.foreign_net | type == "number")' ;;
         "ownership discover"*)
             echo 'type == "array" and length > 0 and (.[0].pdf_url | type == "string")' ;;
         "ownership releases")
@@ -194,6 +200,12 @@ run_case() {
     echo "     PASS"
 }
 
+# A command the --compare binary may predate runs on the new binary only.
+run_new_case() {
+    local COMPARE_BIN=""
+    run_case "$@"
+}
+
 if (( ! DRY_RUN )); then
     command -v jq >/dev/null 2>&1 || { echo "jq is required; run inside nix develop" >&2; exit 1; }
     mkdir -p "$LOG_DIR"
@@ -217,6 +229,10 @@ if selected stocks; then
     run_case compare "stocks compare $SYMBOL,BBRI"
     # BUMI/ADRO/AIMS return non-finite MSN key ratios (Infinity/NaN).
     run_case compare-nonfinite "stocks compare BUMI,ADRO,AIMS"
+    # Broker summaries (IPOT) and foreign flow (IDX, via curl-impersonate).
+    run_new_case broker "stocks broker $SYMBOL"
+    run_new_case bandar "stocks bandar $SYMBOL,BBRI,TLKM"
+    run_new_case flow "stocks flow $SYMBOL --days 3"
 fi
 
 if selected ownership; then