feat(playground): alur interaktif Run→prompt→jawab + file tree collapsible & dukungan .h
- store: normalisasi lifecycle sesi (runStatus/runSessionId/outputCursor/runError,
stdinQueue tetap untuk kompatibilitas)
- +page.svelte: session controller — start, polling recursive setTimeout non-overlap,
delta output via cursor, stop + cleanup unmount/generation counter
- ConsolePanel.svelte: input interaktif (onSendInput/onStop async, mode antrean vs kirim)
- FileTree.svelte: validasi rename (foo.h diterima di C), tombol + langsung mode rename,
collapsible shell dengan handle persisten
- playground-files.ts: validasi nama file (basename, traversal, duplikat case-insensitive)
- api.ts/compiler.ts: client sesi interaktif
- tests: playground.test.ts + playground-files.test.ts
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