Remove tool_choice agent option - auto-detect based on workspace/skills/memory

- Remove tool_choice from AgentEndpoint (create, update, list responses)
- ChatService: automatically set tool_choice='any' when workspace, memory
  or skills present, null otherwise. Same for preparer/review/finalizer
- SystemPromptBuilder: remove 3 toolAny-conditional prompt blocks
  (KRITISCH, Verhalten, ERINNERUNG)
- Frontend: remove checkbox, badge and JS references
- Agent.ToolChoice DB field preserved for backward compat, no longer read

wwwroot/js/cards.js

@@ -99,7 +99,6 @@ function buildAgentCard(agent, skills) {
 
   // Badges
   const badges = [];
-  if (agent.toolChoice === 'any') badges.push('<span class="badge badge-forced-feature" title="Tool-Nutzung erzwingen"><i class="fa fa-wrench"></i> Erzwungen</span>');
   if (agent.allowUserChoice) badges.push('<span class="badge badge-feature" title="Rückfragen per Auswahl erlaubt"><i class="fa fa-question-circle"></i> Rückfragen</span>');
   if (agent.autoCommit === 'mention') badges.push('<span class="badge badge-feature" title="Git-Commits nur auf Anweisung"><i class="fa fa-code-fork"></i> Anmerken</span>');
   if (agent.autoCommit === 'enforce') badges.push('<span class="badge badge-forced-feature" title="Git-Commits nach jeder Änderung erzwungen"><i class="fa fa-code-fork"></i> Erzwungen</span>');

wwwroot/js/pages/agent-page.js

@@ -18,7 +18,6 @@ registerPage('agent', {
     const nameEl = document.getElementById('agentName');
     const descEl = document.getElementById('agentDescription');
     const modelEl = document.getElementById('agentModel');
-    const toolChoiceEl = document.getElementById('agentToolChoice');
     const allowUserChoiceEl = document.getElementById('agentAllowUserChoice');
     const autoCommitEl = document.getElementById('agentAutoCommit');
     const useSoulEl = document.getElementById('agentUseSoul');
@@ -58,7 +57,6 @@ registerPage('agent', {
       nameEl.value = agent.name || '';
       descEl.value = agent.description || '';
       modelEl.value = agent.model || 'sonnet';
-      toolChoiceEl.checked = (agent.toolChoice || 'any') === 'any';
       allowUserChoiceEl.checked = agent.allowUserChoice !== false;
       _agentTaskMde.value(agent.taskInstruction || '');
       autoCommitEl.value = agent.autoCommit || '';
@@ -101,7 +99,6 @@ registerPage('agent', {
         name: nameEl.value.trim() || 'Unbenannt',
         description: descEl.value.trim(),
         model: modelEl.value,
-        toolChoice: toolChoiceEl.checked ? 'any' : 'auto',
         allowUserChoice: allowUserChoiceEl.checked,
         autoCommit: autoCommitEl.value,
         useSoul: useSoulEl.checked,