feat(web): idx website and user docs (Astro Starlight)

Landing page plus docs for install, quickstart, config, the stocks and
ownership CLI, output and exit codes, the MCP server and per-agent setup,
agent usage, and an agent-led install page (agents/install.md) that a
coding agent follows from a one-line prompt.

- Every docs page is also served as Markdown at <path>.md; llms.txt and
  llms-full.txt come from starlight-llms-txt; a SKILL.md for skill-based
  harnesses is under /skills/idx/.
- The CLI reference and MCP tools pages are generated from idx --help and
  the tools golden; a new web-generated flake check fails when they drift.
- nix develop .#web provides bun; Cloudflare Pages builds web/ on pushes.
- Package homepage metadata points at https://idx.rasyidanaf.com.
- .cloudflare/ (the cf CLI's account cache) is git-ignored.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/public/skills/idx/SKILL.md

@@ -0,0 +1,37 @@
+---
+name: idx
+description: Indonesian stock market (IDX) quotes, fundamentals, technicals, screening, and KSEI shareholder ownership through the `idx` CLI. Use for questions about IDX-listed stocks (tickers like BBCA, BBRI, TLKM), who owns them, or ownership changes.
+---
+
+# idx
+
+`idx` is installed as a CLI. Docs: https://idx.rasyidanaf.com (any page as Markdown: add `.md`).
+
+## Rules
+
+- Capture output: it is JSON whenever stdout is not a terminal. Parse it; don't scrape tables.
+- On failure stdout is empty and stderr is `{"error":true,"code":"...","message":"..."}`.
+  Exit `2` fix the input, `3` not found or no cached data, `4` provider unavailable (retry later), `5` unsupported.
+- Tickers are IDX codes (`BBCA`); `.JK` is optional. `stocks quote` and `stocks compare` take several.
+- Ownership data is local. If an ownership command says the database is empty, run `idx ownership sync` once.
+- Ownership percentages are basis points: `5494` = 54.94%.
+
+## Commands
+
+```bash
+idx stocks quote BBCA BBRI                  # price, change, volume, 52-week range
+idx stocks history BBCA --period 1y         # OHLCV; --interval 1d|1wk|1mo
+idx stocks technical BBCA                   # trend, RSI, MACD, moving averages
+idx stocks fundamental BBCA                 # growth, valuation, risk ratings
+idx stocks compare BBCA BBRI BMRI
+idx stocks profile BBCA                     # also: financials, earnings, sentiment, insights, news
+idx stocks screen --filter high-dividend    # top-performers, worst-performers, low-pe, 52w-high, 52w-low, high-volume, large-cap
+
+idx ownership ticker BBCA                   # holders above 1%, concentration, free float
+idx ownership entity "ANTHONI SALIM"        # one investor's holdings
+idx ownership search salim                  # find investor names
+idx ownership releases                      # available months, newest first
+idx ownership changes --from 2026-08-31 --to 2026-09-30
+```
+
+Run `idx <command> --help` for every flag.