fix(editor+agent): multilignes conservees (cause reelle) + validation des modeles Nvidia

Editeur:
- sync() lisait el.textContent qui supprime les <br> : ajout de gt()
  (innerText) utilise par sync(), tableaux (toggle/columns) et _resultText.
- Scission sur Entree + limites haut/bas de bloc via splitCaret() (marqueur
  temporaire au curseur), plus de perte de fin de bloc multi-lignes.

Agent:
- fetch_provider_models() valide la liste nvidia : filtre des modeles
  non-chat (nom) puis probe reelle /chat/completions (6 paralleles, 6s),
  seuls les modeles 2xx restent. 429 conserve (route, donc utilisable).
- Repli sur la liste filtree si toutes les validations echouent.
- tests/test_llm_config.py : 5 cas (catalogue mock, 404 chat, autres
  providers non valides, chute de securite, offline). 276 tests passent.

app/templates/_page_editor_scripts.html

@@ -15,6 +15,16 @@
 
     let _bid=0;function genId(){return 'b'+(++_bid)+'_'+Date.now().toString(36);}
     function cp(e){const s=window.getSelection();if(!s.rangeCount)return 0;const r=s.getRangeAt(0).cloneRange();r.selectNodeContents(e);r.setEnd(s.getRangeAt(0).endContainer,s.getRangeAt(0).endOffset);return r.toString().length;}
+    function gt(e){return (e&&e.innerText!==undefined)?e.innerText:(e?e.textContent:'');}
+    function splitCaret(e){
+      const s=window.getSelection(); if(!s.rangeCount||!s.rangeCount)return null; const sel=s.getRangeAt(0);
+      const MK='\uF000FD'; const mark=document.createElement('span'); mark.textContent=MK;
+      sel.insertNode(mark);
+      const full=gt(e)||'';
+      const parts=full.split(MK);
+      mark.remove(); e.normalize();
+      return {before:parts[0]||'',after:(parts.length>1?parts[1]:'')||'',content:full.split(MK).join('')};
+    }
     function ce(e){const r=document.createRange();r.selectNodeContents(e);r.collapse(false);window.getSelection().removeAllRanges();window.getSelection().addRange(r);}
     function cs(e){const r=document.createRange();r.selectNodeContents(e);r.collapse(true);window.getSelection().removeAllRanges();window.getSelection().addRange(r);}
     function esc(s){return s.replace(/&/g,'&amp;').replace(/</g,'&lt;').replace(/>/g,'&gt;');}
@@ -339,7 +349,7 @@
       _err(msg){ this._html='<p style="color:#e5484d">⚠ '+esc(msg)+'</p>'; this._stage='result'; this.paint(); },
       insert(){ const E=window.E; if(!E||typeof E.applyAIBlocks!=='function')return; E.sync();
         const result=this._resultText(); if(!result)return; E.applyAIBlocks(result); E.dirty=true; E.autoSave(); this.close(); },
-      _resultText(){ const el=this.ROOT&&this.ROOT.querySelector('.aici-result'); return el?el.textContent:''; },
+      _resultText(){ const el=this.ROOT&&this.ROOT.querySelector('.aici-result'); if(!el)return ''; const r=document.createRange();r.selectNodeContents(el);return r.toString(); },
       toast(m){ if(window.showToast)window.showToast(m,'info'); }
     };
     window.AIC=AIC;
@@ -741,9 +751,9 @@
         sync(){const ct=document.getElementById('_blocksCt');if(!ct)return;for(const b of this.blocks){if(b.type==='table'){const wrap=ct.querySelector(`[data-bid="${b.id}"].ftable-editor`);if(wrap){const rows=[];wrap.querySelectorAll('tr.ftable-row').forEach(function(tr){const cells=tr.querySelectorAll('th.ftable-cell,td.ftable-cell');if(!cells.length)return;const rowarr=[];cells.forEach(function(cell){rowarr.push(cell.textContent||'');});rows.push(rowarr);});if(rows.length)b.rows=rows;}continue;}
           if(b.type==='divider'||b.type==='image'||b.type==='embed'||b.type==='table_of_contents')continue;
           if(b.type==='math'){const te=ct.querySelector(`[data-math-bid="${b.id}"]`);if(te)b.content=te.value||'';continue;}
-          const el=ct.querySelector(`[data-bid="${b.id}"]`);if(el&&!el.classList.contains('toggle-title'))b.content=el.textContent||'';else if(el)b.content=el.textContent||'';
-          if(b.type==='toggle'&&b.children)b.children.forEach(function(ch){const che=ct.querySelector(`[data-bid="${ch.id}"]`);if(che)ch.content=che.textContent||'';});
-          if(b.type==='columns'&&b.children)b.children.forEach(function(ch){const che=ct.querySelector(`[data-bid="${ch.id}"]`);if(che)ch.content=che.textContent||'';});
+          const el=ct.querySelector(`[data-bid="${b.id}"]`);if(el&&!el.classList.contains('toggle-title'))b.content=gt(el)||'';else if(el)b.content=gt(el)||'';
+          if(b.type==='toggle'&&b.children)b.children.forEach(function(ch){const che=ct.querySelector(`[data-bid="${ch.id}"]`);if(che)ch.content=gt(che)||'';});
+          if(b.type==='columns'&&b.children)b.children.forEach(function(ch){const che=ct.querySelector(`[data-bid="${ch.id}"]`);if(che)ch.content=gt(che)||'';});
         }},
         render(){const ct=document.getElementById('_blocksCt');if(!ct)return;let html='';for(let i=0;i<this.blocks.length;i++)html+=renderBlock(this.blocks[i],i);ct.innerHTML=html;
          // Render math blocks with KaTeX
@@ -1120,7 +1130,8 @@ applyAIBlocks(text){
           if(e.key==='Enter'){
             if(e.shiftKey){this.dirty=true;this.autoSave();return;}
             e.preventDefault();
-            const text=el.textContent||'',pos=cp(el),before=text.substring(0,pos),after=text.substring(pos);
+            const sp=splitCaret(el);
+            const before=sp?sp.before:gt(el)||'',after=sp?sp.after:'';
             if(!before.trim()&&!after.trim()){
               const nt=(block.type==='bulleted_list'||block.type==='numbered_list'||block.type==='to_do')?block.type:'paragraph';
               this.sync();this.blocks.splice(idx+1,0,this.mkB(nt,''));this.render();
@@ -1132,8 +1143,8 @@ applyAIBlocks(text){
             setTimeout(()=>{const ne=this.getEl(this.blocks[idx+1]?.id);if(ne){ne.focus();cs(ne);}},60);
             this.dirty=true;this.autoSave();return;
           }
-          if(e.key==='ArrowUp'){if(cp(el)===0&&idx>0){e.preventDefault();const prev=this.getEl(this.blocks[idx-1]?.id);if(prev){prev.focus();ce(prev);}}return;}
-          if(e.key==='ArrowDown'){if(cp(el)>=(el.textContent||'').length&&idx<this.blocks.length-1){e.preventDefault();const next=this.getEl(this.blocks[idx+1]?.id);if(next){next.focus();cs(next);}}return;}
+          if(e.key==='ArrowUp'){const _sp=splitCaret(el);if(_sp&&!_sp.before.trim()&&idx>0){e.preventDefault();const prev=this.getEl(this.blocks[idx-1]?.id);if(prev){prev.focus();ce(prev);}}return;}
+          if(e.key==='ArrowDown'){const _sp=splitCaret(el);if(_sp&&!_sp.after.trim()&&idx<this.blocks.length-1){e.preventDefault();const next=this.getEl(this.blocks[idx+1]?.id);if(next){next.focus();cs(next);}}return;}
           if(e.key==='Backspace'){if(!(el.textContent||'').trim()){this.sync();if(block.type!=='paragraph'){e.preventDefault();block.type='paragraph';block.content='';this.render();setTimeout(()=>{const ne=this.getEl(block.id);if(ne)ne.focus();},60);}else if(this.blocks.length>1){e.preventDefault();this.removeBlock(idx);}}return;}
           if(e.key===' '){const b2=bid;setTimeout(()=>this.checkMd(b2),15);}
           if((e.ctrlKey||e.metaKey)&&!e.altKey){const m={b:'bold',i:'italic',u:'underline'};if(m[e.key]){e.preventDefault();document.execCommand(m[e.key]);this.dirty=true;this.autoSave();}}