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/astro.config.mjs

@@ -0,0 +1,65 @@
+// @ts-check
+import { defineConfig } from 'astro/config';
+import starlight from '@astrojs/starlight';
+import starlightLlmsTxt from 'starlight-llms-txt';
+
+export default defineConfig({
+	site: 'https://idx.rasyidanaf.com',
+	integrations: [
+		starlight({
+			title: 'idx',
+			description:
+				'Indonesian stock market (IDX) data and KSEI shareholder ownership, from the terminal or an AI agent through MCP.',
+			logo: { light: './src/assets/wordmark-light.svg', dark: './src/assets/wordmark-dark.svg', alt: 'idx', replacesTitle: true },
+			favicon: '/favicon.svg',
+			social: [{ icon: 'github', label: 'GitHub', href: 'https://github.com/0xrsydn/idx-cli' }],
+			editLink: { baseUrl: 'https://github.com/0xrsydn/idx-cli/edit/main/web/' },
+			customCss: [
+				'@fontsource/ibm-plex-sans/400.css',
+				'@fontsource/ibm-plex-sans/600.css',
+				'@fontsource/jetbrains-mono/400.css',
+				'./src/styles/theme.css',
+			],
+			components: {
+				PageTitle: './src/components/PageTitle.astro',
+			},
+			sidebar: [
+				{
+					label: 'Start',
+					items: ['start/install', 'start/quickstart', 'start/config'],
+				},
+				{
+					label: 'CLI',
+					items: ['cli/stocks', 'cli/ownership', 'cli/output', 'cli/reference'],
+				},
+				{
+					label: 'MCP server',
+					items: [
+						{ label: 'Overview', slug: 'mcp' },
+						'mcp/setup',
+						'mcp/tools',
+					],
+				},
+				{
+					label: 'For agents',
+					items: [
+						{ label: 'Using idx from an agent', slug: 'agents' },
+						'agents/install',
+						{ label: 'llms.txt', link: '/llms.txt' },
+					],
+				},
+				'about',
+			],
+			plugins: [
+				starlightLlmsTxt({
+					projectName: 'idx-cli',
+					details: [
+						'- `idx` is a CLI; `idx-mcp` is an MCP server over the same library. Both read the same config, cache and ownership database.',
+						'- Output is JSON whenever stdout is not a terminal. Errors are one JSON object on stderr; exit codes: 2 invalid input, 3 not found, 4 upstream unavailable, 5 unsupported, 1 other.',
+						'- Every page is also available as Markdown by appending `.md` to its path, for example `/agents/install.md`.',
+					].join('\n'),
+				}),
+			],
+		}),
+	],
+});