feat: bandarmology (idx stocks bandar, analyze_bandar)

`idx stocks bandar SYMBOL...` reads the broker summary: for the top 1, 3,
5 and 10 brokers per side, buy value minus sell value in basis points of
value traded, with a signal from big accumulation to big distribution on
the headline tier (--top, default 5). Several symbols give a screen ranked
by that figure (at most 100, one request each), which pipes from
`stocks screen`. The MCP server exposes it as analyze_bandar (20 symbols).

- analysis/bandar.rs is pure and versioned (`top_concentration_v1`):
  integer basis points, no figure missing counted as zero, buy/sell VWAP
  from exact averages, and the brokers on both sides listed because their
  gross figures overstate their direction.
- Thresholds (±5%/±15%) follow fzn0x/idx (MIT); docs call them heuristics.
- Invalid input fails a screen at once; other errors fail one symbol and
  are warned about on stderr.

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

flake.nix

@@ -288,7 +288,7 @@
                 echo '{"jsonrpc":"2.0","id":2,"method":"tools/list"}'
                 sleep 2
               } | timeout 30 ${mcpPackage}/bin/idx-mcp > out.jsonl
-              jq -se 'map(select(.id == 2))[0].result.tools | length == 12' out.jsonl
+              jq -se 'map(select(.id == 2))[0].result.tools | length == 13' out.jsonl
               touch "$out"
             '';
           # The website's generated pages match the CLI help and the MCP