fix(store): localised docs, debounced typing, explicit-submit always AI

Three Stefan-found bugs in one pass:

1. Documentation rendered in English even when Studio was set
   to German. _loadDocs now passes Localizations.localeOf(...)
   to fetchModuleDocs(); the hub tries README.de.md before
   README.md when locale='de'.

2. 'Keine Treffer' flickered on every keystroke. _onAskTyping
   used to call _runSearch synchronously per character — a
   short 2-3-letter substring matched nothing, so the empty-
   state showed for a frame, then the next character revealed
   results. Add a 250ms typing debounce (Timer + cancel on
   dispose) so the search only re-runs once typing pauses.

3. Submit button did substring search even when System-AI was
   enabled — the _looksLikeQuestion heuristic only routed
   4+-word / question-mark queries through the LLM. The user
   reasonably expected an explicit submit (with the AI-icon
   showing on the button) to actually use AI. New behaviour:
   when system-AI is enabled, the submit button always calls
   _runAiQuery; live-typing keeps substring filtering. The
   heuristic helper was removed (now unused).

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/data/hub.dart

@@ -350,8 +350,8 @@ class HubService {
   /// back as `errorKind` strings (not exceptions) so callers can
   /// render fallback UI without try/catch ceremony.
   Future<({String errorKind, String text, String sourceUrl})>
-      fetchModuleDocs(String name) async {
+      fetchModuleDocs(String name, {String locale = ''}) async {
-    final r = await _client.fetchModuleDocs(name);
+    final r = await _client.fetchModuleDocs(name, locale: locale);
     return (
       errorKind: r.errorKind,
       text: r.text,

lib/pages/store.dart

@@ -5,6 +5,7 @@
 // renders the full bilingual description, requires-list, and
 // repository link.
 
+import 'dart:async';
 import 'dart:convert';
 
 import 'package:flutter/material.dart';
@@ -74,6 +75,11 @@ class _StorePageState extends State<StorePage> {
   List<_AiMatch>? _aiMatches;
   Set<String>? _aiMatchedNames;
   String? _aiError;
+  /// Debounce-Timer für Such-Filterung beim Tippen. Ohne
+  /// Debounce flackert "Keine Treffer" zwischen Buchstaben
+  /// (für 2-3 Buchstaben matched z.B. nichts, das nächste
+  /// dann doch). 250ms ist comfortable für Tippen.
+  Timer? _typingDebounce;
   /// Whether the operator has a System-AI configured. Drives
   /// the Ask-bar hint copy and disables the AI path when off.
   bool _systemAiEnabled = false;
@@ -105,6 +111,7 @@ class _StorePageState extends State<StorePage> {
 
   @override
   void dispose() {
+    _typingDebounce?.cancel();
     _queryCtrl.dispose();
     super.dispose();
   }
@@ -442,7 +449,6 @@ class _StorePageState extends State<StorePage> {
   /// operator submits — otherwise typing "ein Modul, das …"
   /// wipes the visible result set with every space.
   void _onAskTyping(String value) {
-    final trimmed = value.trim();
     if (_aiAnswer != null || _aiMatches != null) {
       setState(() {
         _aiAnswer = null;
@@ -451,17 +457,35 @@ class _StorePageState extends State<StorePage> {
         _aiError = null;
       });
     }
-    if (_systemAiEnabled && _looksLikeQuestion(trimmed)) return;
+    // Tippen läuft IMMER nur durch die lokale Substring-Suche.
-    _runSearch();
+    // Die KI-Suche kostet einen LLM-Roundtrip und gehört hinter
+    // den expliziten Submit-Knopf — sonst feuern wir pro
+    // Keystroke einen Prompt. Debounce verhindert "Keine
+    // Treffer" zwischen Buchstaben.
+    _typingDebounce?.cancel();
+    _typingDebounce = Timer(const Duration(milliseconds: 250), () {
+      if (!mounted) return;
+      _runSearch();
+    });
   }
 
   Future<void> _onAskSubmit() async {
+    // Pending typing-debounce abbrechen — wir submitten jetzt
+    // explizit und wollen nicht hinterher nochmal substring-
+    // filter laufen lassen.
+    _typingDebounce?.cancel();
     final q = _queryCtrl.text.trim();
     if (q.isEmpty) {
       _clearQuery();
       return;
     }
-    if (_systemAiEnabled && _looksLikeQuestion(q)) {
+    // Wenn System-AI verfügbar ist, geht der explizite Submit
+    // IMMER über die KI-Suche — egal ob die Eingabe wie eine
+    // Frage aussieht. Das war der Bug: Nutzer tippt "tabellen"
+    // + klick Suchen, erwartet KI, bekommt Substring-Filter.
+    // Substring-Filter passiert weiter live beim Tippen
+    // (siehe _onAskTyping).
+    if (_systemAiEnabled) {
       await _runAiQuery(q);
     } else {
       _runSearch();
@@ -479,16 +503,6 @@ class _StorePageState extends State<StorePage> {
     _runSearch();
   }
 
-  /// Heuristic question detector — kept generous so a sentence
-  /// "modul für tabellen lesen" triggers the LLM path even
-  /// without a question mark. Single-word and two-word inputs
-  /// stay on substring search where they belong.
-  bool _looksLikeQuestion(String q) {
-    if (q.endsWith('?')) return true;
-    final words = q.split(RegExp(r'\s+'));
-    return words.length >= 4;
-  }
-
   Future<void> _runAiQuery(String query) async {
     setState(() {
       _aiThinking = true;
@@ -1922,10 +1936,14 @@ class _StoreDetailSheetState extends State<_StoreDetailSheet> {
 
   void _loadDocs() {
     if (_docsLoaded) return;
+    // Sprache vom aktuellen Studio-Locale ans Hub weitergeben,
+    // damit `README.de.md` zuerst probiert wird wenn Studio auf
+    // Deutsch steht.
+    final locale = Localizations.localeOf(context).languageCode;
     setState(() {
       _docsLoaded = true;
       _docsFuture =
-          HubService.instance.fetchModuleDocs(widget.item.name);
+          HubService.instance.fetchModuleDocs(widget.item.name, locale: locale);
     });
   }