docs(website): hint feature docs + cast (content for c84a640)

Completes the preceding empty-rename commit: the getting-help "Hints"
section — F1 for a tier-3 teaching hint on the live input, `hint` to
explain the most recent error — with the real rendered block and a cast
showing both (the live-input hint via the demo-mode Ctrl-G→[F1] alias,
since autocast can't send F1, then `hint` on an error). the-assistive-editor
points at F1; CtrlG added to the cast generator's key map.

website/casts-src/casts.mjs

@@ -266,6 +266,33 @@ export const casts = [
       { key: 'CtrlC' }, // quit invisibly (Ctrl-C) — cast ends on the last content frame
     ],
   },
+  {
+    name: 'hint',
+    title: 'Ask for a hint — on the command you are typing, or on the last error',
+    width: 90,
+    // Taller: the tier-3 hint blocks (What / Example / Concept) plus the command
+    // echoes need the room. The live-input hint is opened with Ctrl-G, which in
+    // --demo mode aliases F1 and badges AS [F1] (ADR-0047 Amendment 1) — autocast
+    // can't send F1 (an escape sequence), so this control byte stands in for it.
+    height: 30,
+    typeSpeed: '45ms',
+    steps: [
+      { wait: 1000 },
+      { type: 'create table customers with pk id(serial)', after: 650 },
+      { type: 'add column to customers: email (text)', after: 850 },
+      // Live-input hint: type a command but DON'T submit, then Ctrl-G (badged
+      // [F1]) opens a teaching hint for the command being built.
+      { type: "insert into customers (email) values ('ada@example.io')", enter: false, after: 1500 },
+      { key: 'CtrlG', after: 3400 }, // [F1] badge + the insert hint block — hold to read
+      { key: 'Enter', after: 2000 }, // the buffer is intact → submit the insert
+      // Error-recovery hint: a command that fails, then `hint` explains it.
+      { type: 'show data orders', after: 2200 }, // no such table → friendly error
+      { type: 'hint', enter: false, after: 1200 },
+      { key: 'Enter', after: 3400 }, // the error hint block — hold to read
+      { caption: 'A hint for what you are typing, or for the last error.', after: 3200 },
+      { key: 'CtrlC' }, // quit invisibly (Ctrl-C) — cast ends on the last content frame
+    ],
+  },
   {
     name: 'quickstart',
     title: 'RDBMS Playground — first table to first query',

website/casts-src/generate.mjs

@@ -49,6 +49,11 @@ const NAMED_KEYS = {
   CtrlO: '^O',
   // Esc leaves navigation mode directly (back to the input field).
   Esc: '^[',
+  // Ctrl-G: in demo mode the app aliases this to F1 (the contextual-hint key,
+  // ADR-0053) and badges it AS [F1] (ADR-0047 Amendment 1). autocast can't emit
+  // F1 (an escape sequence), but it can send this single control byte — so a
+  // cast can show the live-input hint exactly as a real F1 press would.
+  CtrlG: '^G',
 };
 
 /** Build the autocast `keys:` list (one entry per line) for a cast's steps. */