feat: bandar and broker totals for one investor side

IPOT's investor filter splits each broker row by client domicile, but its
footer then gives only that side's buying (BBCA 2026-10-16: foreign 1.7 T,
domestic 4.9 T of 6.6 T). The foreign net gives the selling on all boards:
foreign 1.7 + 2.3 = 4.0 T (IDX: about 3.95 T regular), domestic
4.9 - 2.3 = 2.6 T.

- BrokerSummary gains buy_value and sell_value: the total for all
  investors, the footer and the derived selling for one side (selling is
  null with a board filter, where the net covers other boards).
- Bandar weighs the top N buyers' share of the value bought against the
  top N sellers' share of the value sold, so `--investor foreign|domestic`
  reads that side alone; for all investors the readings are unchanged.
  One side on one board is refused, as there is no selling to weigh.
- Tables print what the side bought and sold; fixtures for foreign and
  domestic on all boards were recorded from IPOT.

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

crates/idx-mcp/tests/golden/tools.json

@@ -1,6 +1,6 @@
 [
   {
-    "description": "Bandarmology for one or more IDX tickers from the broker summary: for the top 1, 3, 5 and 10 brokers per side, buy value minus sell value as basis points of value traded (`imbalance_bps`), with a `signal` from big_accumulation (>= +1500) through neutral (within +-500) to big_distribution (<= -1500), headlined by `top` (default 5). Reports come strongest accumulation first; tickers that fail are listed under `failures`. A heuristic over end-of-day broker codes: brokers trade for many clients, and `both_sides` lists brokers whose gross figures overstate their direction. `method` names the rules applied. `investor` must be `all`: the summary has no total for one investor side.",
+    "description": "Bandarmology for one or more IDX tickers from the broker summary: for the top 1, 3, 5 and 10 brokers per side, buy value minus sell value as basis points of value traded (`imbalance_bps`), with a `signal` from big_accumulation (>= +1500) through neutral (within +-500) to big_distribution (<= -1500), headlined by `top` (default 5). Reports come strongest accumulation first; tickers that fail are listed under `failures`. A heuristic over end-of-day broker codes: brokers trade for many clients, and `both_sides` lists brokers whose gross figures overstate their direction. `method` names the rules applied. With `investor` foreign or domestic, shares are of that side's own buying (`buy_value`) and selling (`sell_value`); that needs `board` all.",
     "inputSchema": {
       "$schema": "https://json-schema.org/draft/2020-12/schema",
       "properties": {
@@ -134,7 +134,7 @@
     "name": "compare_stocks"
   },
   {
-    "description": "Broker summary for one IDX ticker: the top 10 buyers and top 10 sellers by lots over a session or date range, each with lots (1 lot = 100 shares), value and average price in IDR, plus totals. Buyers and sellers are ranked separately and gross, so a broker can appear on both sides. End of day only (IDX hides broker codes during trading); `kind` is the broker's own status (local, foreign, state_owned), not its clients'. `rounded` = true means figures of a million and more carry one decimal of precision.",
+    "description": "Broker summary for one IDX ticker: the top 10 buyers and top 10 sellers by lots over a session or date range, each with lots (1 lot = 100 shares), value and average price in IDR, plus totals. Buyers and sellers are ranked separately and gross, so a broker can appear on both sides. End of day only (IDX hides broker codes during trading); `kind` is the broker's own status (local, foreign, state_owned), not its clients'. With `investor` foreign or domestic, each row is that broker's foreign or domestic clients' trades, `total_value` is null, and `buy_value`/`sell_value` give what that side bought and sold (`sell_value` needs `board` all). `rounded` = true means figures of a million and more carry one decimal of precision.",
     "inputSchema": {
       "$schema": "https://json-schema.org/draft/2020-12/schema",
       "properties": {