Fix AI Literacy Course lesson-item ordering

[hal-eisen-adfa]

Problem

The AI Literacy Course presented lesson items in the wrong order — it did not match the numbered sequence in the course bundle (1-objectives.mp4, 2-what-is-ai.mp4, … 7-lesson-1-worksheet.zip).

Root cause

CourseShell.itemsOf() sorted with compareBy({ leadingNumber(it.title) }, { it.title }), but Item.title had already had its N- ordering prefix stripped by itemTitle(). The old leadingNumber regex (\d+) then matched the first digit anywhere in the stripped title. Two failures compounded:

• Genuinely-first items like 1-objectives → "Objectives" had no digit left → Int.MAX_VALUE → sorted last.
• Items whose text contains a number, e.g. 5-lesson-1-recap-quiz → "Lesson 1 Recap Quiz", picked up the embedded 1 → sorted first.

Result for Lesson 1 (buggy): Project Time → Recap Quiz → Worksheet → AI Or Not Quiz → How AI Can Help Us → Objectives → What Is AI.

Section-level ordering was already correct (sectionOrder() keys off the raw folder name); only intra-section item order was broken.

Fix

• Add order: Int to Item, computed via leadingNumber(...) from the original file/dir name (before itemTitle() strips the prefix), and sort by it.order then title.
• Anchor leadingNumber to ^(\d+) so it can only read the leading ordering prefix, never a digit embedded later in the name.

After the fix, Lesson 1 renders: Objectives → What Is AI → AI Or Not Quiz → How AI Can Help Us → Lesson 1 Recap Quiz → Lesson 1 Project Time → Lesson 1 Worksheet.

CourseShell.generate() only runs during CourseInstaller.ensureInstalled(), which is gated by an install-version marker, so INSTALL_VERSION is bumped 2 → 3 to force existing installs to re-extract and regenerate index.html with the corrected order.

Verification

• Ported the exact old vs. new sort to a mock lesson tree: BEFORE reproduced the scramble, AFTER matched the numeric-prefix order exactly.
• Built the .cgp and installed on device (Samsung S22). Confirmed lessons now list items in numbered order. (Surfaced and fixed a separate pre-existing issue in the process: pdfjs.zip is a build-time downloaded asset, and a bare assemblePlugin without a prior downloadAssets ships a viewer-less .cgp; re-fetched before the device test — see note below.)

Note / possible follow-up

./gradlew assemblePlugin silently produces a broken plugin if the downloaded assets (pdfjs.zip, ai-literacy-course.zip) aren't present, with no build-time warning — only scripts/update-libs.sh runs downloadAssets first. A follow-up could make assemblePlugin fail fast (or depend on downloadAssets) when those assets are missing. Not included here to keep this PR scoped to the ordering fix.

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