Bitesize Reading Library V4.7.3

WHAT CHANGED
- Improved assessment tracker heading contrast so skill group headings are easy to read.
- Fixed native core-reading presentation sizing so full-screen slides fit inside the available screen without horizontal or vertical scrolling.
- Added first-use Standards Coverage guide explaining Addressed, Practised and Assessed, the coverage matrix and how to interpret gaps.
- Added first-use Assessment guide explaining class setup, 1/0 marking, mark schemes, profiles/progress and why digital escape rooms remain standards practice rather than fixed assessments.
- Both guides include a 'Don't show this guide automatically again' choice and can always be reopened from a Guide button.

COMPATIBILITY
- Existing classes, marks, imported resources and V4.7.2 escape-room migration behaviour are preserved.
- Core reading comprehension resources retain formal mark-based assessment.
- Standards-practice escape rooms remain excluded from formal assessment unless explicitly declared formal.
