docs(quick-260329-ten): complete leertaste symbol in entdecken-phase plan

.planning/quick/260329-ten-leertaste-symbol-in-entdecken-phase-erkl/260329-ten-SUMMARY.md

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+---
+phase: quick
+plan: 260329-ten
+subsystem: ui/screens
+tags: [discover-phase, space-bar, ux, level-1]
+dependency_graph:
+  requires: []
+  provides: [space-bar-discover-step]
+  affects: [runDiscoverPhase, level-1-lesson-flow]
+tech_stack:
+  added: []
+  patterns: [DOM manipulation, keyboard event listener, CSS class toggle]
+key_files:
+  modified:
+    - src/ui/screens.ts
+decisions:
+  - Space bar discover step uses hardcoded German text (not getLetterIntro) to guarantee ␣ symbol mention
+  - Space key discover step follows identical UX pattern as letter discover steps for consistency
+metrics:
+  duration: "2min"
+  completed: "2026-03-29"
+  tasks: 1
+  files_modified: 1
+---
+
+# Quick Task 260329-ten: Leertaste Symbol in Entdecken-Phase Summary
+
+**One-liner:** Added dedicated space bar discover step showing ␣ symbol with "Leertaste" label and child-friendly explanation before practice begins.
+
+## What Was Done
+
+The `runDiscoverPhase()` function in `src/ui/screens.ts` previously skipped the space key entirely with `if (key === " ") continue`. This meant children encountered the ␣ symbol during practice without any introduction.
+
+The fix replaces the skip with a full discover step for the space bar:
+
+1. Companion text explains the ␣ symbol in child-friendly German: "Siehst du die grosse Taste ganz unten? Das ist die Leertaste! Wenn du dieses Zeichen siehst: ␣ — dann drueckst du mit dem Daumen die Leertaste. Probier es aus!"
+2. The ␣ symbol (U+2423) is displayed large using the `falling-letter` class, with a "Leertaste" label underneath.
+3. The space key on the keyboard is highlighted and pulses with `keyboard__key--discover-pulse`.
+4. Child must press the space bar once to confirm understanding and advance.
+
+## Deviations from Plan
+
+None — plan executed exactly as written.
+
+## Commits
+
+| Task | Name | Commit | Files |
+|------|------|--------|-------|
+| 1 | Add space bar discover step in runDiscoverPhase | 869b1e3 | src/ui/screens.ts |
+
+## Verification
+
+- All 85 existing tests pass (7 test files).
+- No regressions introduced.
+
+## Self-Check: PASSED