P18 phase 1: one console and Stop (IDE and embed, protocol v4) - #29

Phase 1 of P18 (spec: teaching-agent journal.md → Visual Identity → «glpython-IDE (Hülle um den Editor)»): behaviour in the IDE and the embed.

Stop

• While Python is busy for more than 300 ms, ▶ Ausführen becomes ■ Stoppen. Busy means a program, a REPL input such as endlos(), Tests or a visualization. The 300 ms delay keeps quick REPL inputs from making the button flicker.
• Stopping ends the worker and starts a new one:
  • The code stays.
  • The console keeps what was printed and adds «Gestoppt. Python wurde neu gestartet.» (en: "Stopped. Python was restarted.").
  • The REPL starts in an empty namespace. Earlier entries lose «Visualisieren», since their session is gone.
• Hosts can use command: { type: 'stop' } and the new onBusyChange prop.
• Interrupt without restart is possible where the page is cross-origin isolated (the IDE: Pyodide's setInterruptBuffer → KeyboardInterrupt, keeping the namespace). It is not possible in LiaScript's embed, where the iframe isn't isolated. I kept one behaviour everywhere, the restart, and list the interrupt as a follow-up.

Embed protocol version 4

• glpython:stop (parent → embed).
• glpython:busy {busy} (embed → parent), only to parents that speak version 4.
• capabilities.stop in glpython:ready.
• On a reset, the embed also sends busy: false.
• Earlier versions keep working. check-embed-protocol.mjs covers version 4. embed/demo.html's Run becomes Stop while busy.
• The macro's ▶ → ■ comes in a separate glpython-liascript PR.

One console («Konsole»)

• One transcript: the program's output, then REPL inputs, Tests reports and notes, in the order they happen. A Tests report is now appended instead of replacing the output. Errors and hints stand where they happened. Run and Reset clear it.
• Streamed output: what a program or REPL input prints appears while it runs, not only at the end. The worker sends at most 50 messages per 50 ms and the page applies them every 40 ms, so a printing loop doesn't flood the page. The final result brings the whole output, so nothing is doubled or lost.
• Long output: the console keeps the last 100,000 characters, and follows new output unless the learner has scrolled up.
• In the embed: the console grows with its content up to 480px, then scrolls. Before, a printing loop would have stretched the iframe beyond the macro's 1200px cap.

A bug fixed on the way

A REPL input before any Run (now also right after a stop) failed with ModuleNotFoundError: No module named 'gturtle', because only a Run put / on sys.path. session.py adds it when it loads.

Tested

In the built embed via its protocol, and in the IDE with this build (laptop 1440 and iPad 820 widths):

lint (known warning only), both builds, test:protocol, test:runtime and test:hints pass. Screenshots are in the phase report.

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