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/src/content/docs/start/quickstart.md

@@ -0,0 +1,50 @@
+---
+title: Quickstart
+description: First stock and ownership commands.
+---
+
+## Stocks
+
+Tickers are IDX codes; the `.JK` suffix is optional.
+
+```bash
+idx stocks quote BBCA                 # one quote
+idx stocks quote BBCA BBRI BMRI       # several (spaces or commas)
+idx stocks history BBCA --period 1y   # daily OHLCV
+idx stocks technical BBCA             # trend, RSI, MACD, moving averages
+idx stocks fundamental BBCA           # growth, valuation and risk together
+idx stocks compare BBCA BBRI BMRI     # fundamentals side by side
+idx stocks screen --filter high-dividend
+```
+
+## Ownership
+
+Ownership data comes from the monthly KSEI register of holders above 1%.
+Download the maintained snapshot once; after that every query runs offline.
+
+```bash
+idx ownership sync                    # a few MB, safe to rerun
+idx ownership ticker BBCA             # who holds BBCA
+idx ownership entity "ANTHONI SALIM"  # everything one investor holds
+idx ownership search salim            # find investor names
+idx ownership releases                # which months you have
+idx ownership changes --from 2026-08-31 --to 2026-09-30
+```
+
+## JSON
+
+In a terminal idx prints tables. When its output is piped or captured it
+prints JSON, so scripts and agents need no flag:
+
+```bash
+idx stocks quote BBCA BBRI | jq -r '.[] | "\(.symbol) \(.price)"'
+idx -o json stocks quote BBCA        # force JSON in a terminal
+```
+
+See [Output and exit codes](/cli/output/) for the full contract.
+
+## Next
+
+- [Stocks guide](/cli/stocks/) and [ownership guide](/cli/ownership/)
+- [Configuration](/start/config/)
+- [Use idx from an AI agent](/mcp/setup/)