Add OG social cards, Mermaid diagrams, and robots.txt

- OG images: auto-generated per page via astro-og-canvas with maritime
  teal theme, wired through Starlight route data middleware
- Mermaid: request flow and parallel fetch diagrams on architecture page
- robots.txt: sitemap and llms.txt references for crawlers

docs/astro.config.mjs

@@ -1,4 +1,5 @@
 import { defineConfig } from "astro/config";
+import mermaid from "astro-mermaid";
 import starlight from "@astrojs/starlight";
 import starlightLlmsTxt from "starlight-llms-txt";
 
@@ -10,10 +11,12 @@ export default defineConfig({
   telemetry: false,
   devToolbar: { enabled: false },
   integrations: [
+    mermaid(),
     starlight({
       title: "mcnoaa-tides",
       description:
         "FastMCP server for NOAA CO-OPS tide predictions, water levels, and marine conditions.",
+      routeMiddleware: "./src/routeData.ts",
       plugins: [
         starlightLlmsTxt({
           projectName: "mcnoaa-tides",

docs/package.json

@@ -17,6 +17,8 @@
     "@iconify-json/lucide": "^1.2.91",
     "astro": "^5.6.1",
     "astro-icon": "^1.1.5",
+    "astro-mermaid": "^1.3.1",
+    "astro-og-canvas": "^0.10.1",
     "sharp": "^0.34.2",
     "starlight-llms-txt": "^0.7.0"
   }

docs/public/robots.txt

@@ -0,0 +1,7 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://mcnoaa-tides.warehack.ing/sitemap-index.xml
+
+# LLM documentation — https://llmstxt.org/
+LLMs-Txt: https://mcnoaa-tides.warehack.ing/llms.txt

docs/src/content/docs/understanding/architecture.mdx

@@ -9,6 +9,35 @@ import { Aside, Card, CardGrid, Steps, FileTree, Badge } from "@astrojs/starligh
 
 mcnoaa-tides is a FastMCP server that wraps the NOAA CO-OPS Tides and Currents API. This page describes how the pieces fit together -- the server lifecycle, caching strategy, parallel fetch patterns, and module organization.
 
+## Request Flow
+
+```mermaid
+flowchart LR
+    User([User])
+    LLM[LLM Client]
+    MCP[MCP Transport<br/>stdio / HTTP]
+    Server[mcnoaa-tides<br/>FastMCP Server]
+    Cache[(Station<br/>Cache)]
+    DataAPI[NOAA Data API<br/>Predictions &<br/>Observations]
+    MetaAPI[NOAA Metadata API<br/>Station Catalog]
+
+    User -->|natural language| LLM
+    LLM -->|tool call| MCP
+    MCP --> Server
+    Server -->|cache hit| Cache
+    Server -->|parallel fetch| DataAPI
+    Server -->|catalog refresh| MetaAPI
+    Cache -.->|24h TTL| MetaAPI
+
+    style User fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
+    style LLM fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
+    style MCP fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
+    style Server fill:#1a8a8f,stroke:#5ec4c8,color:#0a1517
+    style Cache fill:#0d3b3e,stroke:#5ec4c8,color:#e8f0f0
+    style DataAPI fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
+    style MetaAPI fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
+```
+
 ## Server Lifecycle
 
 The server uses FastMCP's lifespan context manager to own the `NOAAClient` instance. Every tool call receives the same client through the lifespan context, so there is exactly one HTTP connection pool and one station cache for the entire server process.
@@ -86,9 +115,28 @@ Several tools fire multiple API calls simultaneously using `asyncio.gather`. Thi
 
 Fetches 6 products in parallel:
 
-```
-predictions (hilo) | water_level | water_temperature
-air_temperature    | wind        | air_pressure
+```mermaid
+flowchart LR
+    Tool[marine_conditions<br/>_snapshot]
+    P[predictions<br/>hilo]
+    WL[water_level]
+    WT[water_temperature]
+    AT[air_temperature]
+    W[wind]
+    AP[air_pressure]
+    R[Combined<br/>Response]
+
+    Tool --> P & WL & WT & AT & W & AP
+    P & WL & WT & AT & W & AP --> R
+
+    style Tool fill:#1a8a8f,stroke:#5ec4c8,color:#0a1517
+    style R fill:#1a8a8f,stroke:#5ec4c8,color:#0a1517
+    style P fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
+    style WL fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
+    style WT fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
+    style AT fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
+    style W fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
+    style AP fill:#0d3b3e,stroke:#1a8a8f,color:#e8f0f0
 ```
 
 Each product is fetched independently. If a product fails (sensor not available at the station, temporary API error), it is recorded under an `"unavailable"` key in the response rather than failing the entire request.

docs/src/pages/og/[...slug].ts

@@ -0,0 +1,40 @@
+import { getCollection } from "astro:content";
+import { OGImageRoute } from "astro-og-canvas";
+
+const entries = await getCollection("docs");
+const pages = Object.fromEntries(
+  entries.map(({ data, id }) => [id, { data }]),
+);
+
+export const { getStaticPaths, GET } = await OGImageRoute({
+  pages,
+  param: "slug",
+  getImageOptions: (_id, page: (typeof pages)[number]) => ({
+    title: page.data.title,
+    description: page.data.description,
+    bgGradient: [[10, 21, 23]],
+    border: { color: [26, 138, 143], width: 20 },
+    padding: 120,
+    font: {
+      title: {
+        size: 64,
+        weight: "Bold",
+        color: [232, 240, 240],
+        families: ["Inter"],
+      },
+      description: {
+        size: 28,
+        color: [196, 212, 214],
+        families: ["Inter"],
+      },
+    },
+    fonts: [
+      "https://cdn.jsdelivr.net/fontsource/fonts/inter@latest/latin-600-normal.woff2",
+      "https://cdn.jsdelivr.net/fontsource/fonts/inter@latest/latin-400-normal.woff2",
+    ],
+    logo: {
+      path: "./public/favicon.svg",
+      size: [60],
+    },
+  }),
+});

docs/src/routeData.ts

@@ -0,0 +1,27 @@
+import { defineRouteMiddleware } from "@astrojs/starlight/route-data";
+
+export const onRequest = defineRouteMiddleware((context) => {
+  const ogImageUrl = new URL(
+    `/og/${context.locals.starlightRoute.id || "index"}.png`,
+    context.site,
+  );
+
+  const { head } = context.locals.starlightRoute;
+
+  head.push({
+    tag: "meta",
+    attrs: { property: "og:image", content: ogImageUrl.href },
+  });
+  head.push({
+    tag: "meta",
+    attrs: { property: "og:image:width", content: "1200" },
+  });
+  head.push({
+    tag: "meta",
+    attrs: { property: "og:image:height", content: "630" },
+  });
+  head.push({
+    tag: "meta",
+    attrs: { name: "twitter:image", content: ogImageUrl.href },
+  });
+});