feat(website): pace modes/undo-redo/joins casts (split submits, surface state)

Split the short pivotal commands from their submit so they read before
the screen changes (`mode advanced` in modes/joins; `undo`/`redo` before
their confirm modals), and surface the source tables in joins with
`show data` before the join, since the schema sidebar is hidden at 90 cols.

website/casts-src/casts.mjs

@@ -116,7 +116,10 @@ export const casts = [
       { type: "insert into books (title) values ('A Wizard of Earthsea')", after: 650 },
       { type: "insert into books (title) values ('Invisible Cities')", after: 1100 },
       { type: 'show data books', after: 1600 }, // simple mode — no SQL echo
-      { type: 'mode advanced', after: 1300 },
+      // Split the mode switch (type → beat → submit) so the short, pivotal
+      // command reads before the screen changes.
+      { type: 'mode advanced', enter: false, after: 1100 },
+      { key: 'Enter', after: 1300 },
       { type: 'show data books', after: 2400 }, // advanced — shows "Executing SQL: …"
       { key: 'CtrlC' }, // quit invisibly (Ctrl-C) — cast ends on the last content frame
     ],
@@ -134,10 +137,14 @@ export const casts = [
       { type: "insert into books (title) values ('A Wizard of Earthsea')", after: 650 },
       { type: "insert into books (title) values ('Invisible Cities')", after: 1100 },
       { type: 'show data books', after: 1500 }, // two rows
-      { type: 'undo', after: 1300 }, // opens the confirmation modal
+      // Split the short command from its submit so `undo` reads before the
+      // confirmation modal pops over it.
+      { type: 'undo', enter: false, after: 1000 },
+      { key: 'Enter', after: 1300 }, // submit → opens the confirmation modal
       { type: 'y', enter: false, after: 1600 }, // Y confirms
       { type: 'show data books', after: 1500 }, // one row
-      { type: 'redo', after: 1200 },
+      { type: 'redo', enter: false, after: 1000 },
+      { key: 'Enter', after: 1300 },
       { type: 'y', enter: false, after: 1600 },
       { type: 'show data books', after: 1700 }, // two rows again
       { key: 'CtrlC' }, // quit invisibly (Ctrl-C) — cast ends on the last content frame
@@ -162,8 +169,13 @@ export const casts = [
       { type: "insert into books (title, author_id) values ('A Wizard of Earthsea', 1)", after: 600 },
       { type: "insert into books (title, author_id) values ('The Left Hand of Darkness', 1)", after: 600 },
       { type: "insert into books (title, author_id) values ('Invisible Cities', 2)", after: 900 },
-      // switch to SQL and join
-      { type: 'mode advanced', after: 1200 },
+      // Surface the two source tables before joining them — at 90 cols the
+      // schema sidebar is hidden, so this is how the viewer sees what's there.
+      { type: 'show data authors', after: 1600 },
+      { type: 'show data books', after: 1900 },
+      // switch to SQL and join (split the mode switch for a readable beat)
+      { type: 'mode advanced', enter: false, after: 1100 },
+      { key: 'Enter', after: 1300 },
       {
         type: 'select authors.name, books.title from books join authors on books.author_id = authors.author_id order by authors.name',
         after: 2600,