Build all apps from Markdown content; Compose Desktop replaces GTK on Linux and Windows

- content/ + scripts/build-content.py produce content.json for every app
- stable lesson IDs with one-time progress migration (Swift, Kotlin)
- shared answer-check tests (tests/answers.json) for Kotlin and Swift
- android/desktop: Compose app with updater, speech and GTK progress import
- CI packages AppImage and Windows zip with ProGuard, runs the tests

Co-authored-by: Cursor <cursoragent@cursor.com>

content/anglictina/2-rocnik/01-na-cestach.md

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+---
+id: anglictina-2-na-cestach
+puvodni: en.2.1
+nazev: Na cestách
+popis: Stupňování a minulý čas průběhový. Doplňování a kvíz.
+---
+
+# Výklad
+
+## Porovnat dvě věci i celou skupinu
+*Stupňování*
+
+- cheap → cheaper → the cheapest. Expensive → more expensive → the most expensive.
+- Nepravidelné: good → better → the best, bad → worse → the worst, far → further → the furthest.
+- as … as: The bus is as fast as the train today.
+- than stojí po komparativu: This hostel is cheaper than the hotel.
+
+> Tip: kratší přídavná jména berou -er/-est, delší more/most.
+
+## Děje, který probíhal, když se stalo něco jiného
+*Past continuous*
+
+- I was reading when the train stopped.
+- While we were waiting, it started to rain.
+- Zápor: We weren't sleeping. Otázka: Were you driving?
+- Nepleťte si ho s minulým prostým: I walked home popisuje celou cestu.
+
+> Tip: průběhový čas je pozadí, prostý je krátká událost.
+
+
+# Doplňování
+
+## This ticket is ___ (cheap) than the night train.
+= cheaper
+> Krátké přídavné jméno: -er.
+
+## It was the ___ (bad) hotel in the town.
+= worst
+> bad, worse, the worst.
+
+## Prague is not as ___ as London.
+= big
+> as + základní tvar + as.
+
+## I ___ (read) when the bus suddenly stopped.
+= was reading
+> Pozadí: past continuous.
+
+## While we ___ (wait), a street musician started to play.
+= were waiting
+> While + průběhový děj.
+
+
+# Kvíz
+
+## far → ___ → the furthest
+- farer
+- [x] further
+- more far
+- farthest only
+> far, further, the furthest. Farthest je taky možné, ale further je v učebnici první.
+
+## Which sentence is correct?
+- This café is more cheap than that one.
+- [x] This café is cheaper than that one.
+- This café is the cheaper than that one.
+- This café is cheap than that one.
+> cheap → cheaper than.
+
+## She ___ a map when she missed the stop.
+- looked
+- [x] was looking
+- looks
+- is looking
+> Dělo se to v okamžiku, kdy zmeškala zastávku.
+
+## good → better → ___
+- the goodest
+- the better
+- [x] the best
+- the most good
+> the best.