fix(views): make boolean view params work, and retune the prompter

The params editor could not represent a boolean which defaults to true.
Two bugs stacked:

- ParamInput fell back with `isStringBoolean(param) ?? defaultValue`, but
  isStringBoolean answers false for an absent param rather than nothing, so
  the ?? never fired and every switch opened off whatever its option said.
- An unchecked checkbox is absent from the form data rather than present and
  false, so switching one off wrote no param and the parser fell back to the
  default the user was trying to leave.

Either one alone is invisible while every boolean defaults to false, which is
why this surfaced with the teleprompter. Together they made the whole panel
look inert: the switch showed off, the view showed on, and Apply did nothing.

Prompter changes from the review:

- Speed is calibrated against the reading rate rather than picked for feel.
  30 lines per minute was about 300 words per minute, roughly twice a
  broadcast read; the default is now 12, measured at 129 wpm on the default
  column. The ceiling comes down from 200 to 40 so the arrows stay useful.
- Smaller, denser defaults: 40px over 1.3 line height in an 80% column, which
  is 21 lines on a 1080p screen where the old defaults gave 11.
- The reading line is a marker one line tall in the gutter beside the text,
  replacing the rule across the words and the pair of margin arrows. The
  option is a boolean now that there is one style rather than three.
- Space always drives the transport. It was deferring to whichever control
  had focus, so a prompter stopped responding to the pedal after anyone
  touched a button; the overlay drops focus after a pointer press instead.
  Enter still activates a focused control, so the overlay stays keyboard
  operable.
- The help dialog is laid out as the rundown shortcuts panel is, down to the
  Kbd keycaps and the grouping, and no longer explains foot pedals.

Headings stay on the same left rail as the script rather than centred: they
are signposts for the operator, and a second alignment would give the eye
something new to find at every segment change.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cb8RVPNQ2ETPJxdy4b8CHf

e2e/tests/utils/seedScript.ts

@@ -0,0 +1,24 @@
+import type { Page } from '@playwright/test';
+
+export const scriptMarker = 'E2E prompter script';
+
+/** long enough that the document scrolls well past a screen */
+export const scriptText = `${scriptMarker}. `.repeat(40);
+
+/**
+ * Puts a known script into whichever rundown happens to be loaded.
+ *
+ * Specs which read the rundown cannot rely on the uploaded fixture surviving:
+ * the suite runs serially and earlier specs add, edit and delete entries, while
+ * 214 creates a fresh rundown and leaves it loaded. Seeding is idempotent, so
+ * the rundown gains one event no matter how many tests have run before.
+ */
+export async function seedScript(page: Page) {
+  const rundown = await (await page.request.get('/data/rundowns/current')).json();
+  const alreadySeeded = rundown.flatOrder.some((id: string) => rundown.entries[id]?.note?.startsWith(scriptMarker));
+  if (alreadySeeded) return;
+
+  await page.request.post(`/data/rundowns/${rundown.id}/entry`, {
+    data: { type: 'event', title: 'Teleprompter e2e', note: scriptText },
+  });
+}