Android: the editor's text reaches the assembler, and the tabs come back

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Two defects found on the emulator while verifying the gjsify link. Both made
the app look finished and do nothing.

The bottom tab bar measured three pixels

Adw.ViewSwitcherBar:reveal defaults to FALSE. In a GNOME window an
Adw.Breakpoint asks for the bar once the window goes narrow, and a wide
window keeps it collapsed in favour of the header-bar switcher. Android has
no wide branch — this shell IS the narrow layout — and nothing ever asked.

The app had no visible way to change page, and the shell measured 1517 px of
a 2400 px screen with white below it. One line, and both symptoms go.

Left: before. Right: after — Lernen / Coden / Debuggen / Spielen back at
the bottom, shell filling the screen.

Assemble ran on an empty program

SourceView.codeProperty.register() at the bottom of source-view.ts does
Object.defineProperty on the prototype, which overwrites the get code() /
set code() written in the class body. Those accessors were dead from the
moment the module loaded, while looking authoritative: reads went to
NativeScript's property store, whose value is defaultValue: "", and typing
changes the inner TextView and never that store.

Measured on the emulator after typing LDA #$01:

read	value
textChange event	"LDA #$01"
textView.text	"LDA #$01"
native getText()	"LDA #$01"
editorController.code	""

The last line is what Assemble assembled. The toast then said only "Assemble
failed" — the assembler's own message never reaches the port — while the same
program assembles headlessly:

$ learn6502 assemble t.asm
Code assembled successfully, 2 bytes.

The typed text goes back into the property now, through
codeProperty.nativeValueChange(): the direction NativeScript provides for
"the native side moved", which does not re-enter valueChanged's write-back
into the widget the value came from. The dead accessors are gone, and a
comment says why the class has none.

Verified

• gjsify workspace @learn6502/app-android run check: exit 0, 0 error TS
• gjsify format --check: "All matched files use the correct format."
• On the emulator: four tabs at the bottom, shell fills the screen, and
  LDA #$01 / STA $0200 / BRK reports "Erfolgreich assembliert" with the
  button switching to Run.

Known, not fixed here

• After the soft keyboard has been shown once, the shell keeps the reduced
  height — tab bar at y=1455 instead of y=2338. Measured, pre-existing.
• The tab icons render as placeholder glyphs.
• The assembler's failure message is dropped: the shared controller emits
  assemble-failure with an AssemblerFailureEvent and the Android port has
  no handler for it, so every failure reads "Assemble failed". That is why
  this defect stayed invisible.

🤖 Generated with Claude Code