fix(bookslm): 422 + thème + picker zindex

- Bug 1 (422): bookslm.js envoie maintenant {message, conversation_history}
  conformes au backend (au lieu de messages:[...])
- Bug 2 (thème BooksLM): style.css lignes 9015-9061 — suppression de
  tous les fallbacks hex (--bg, --muted, --text, --surface, --accent,
  --border) au profit des variables ObsiGate existantes (--bg-primary,
  --text-primary, --text-secondary, --surface, --surface2, --accent,
  --border). Ajout de color: var(--text-primary) sur .bookslm-panel
- Bug 3 (picker zindex/flex): bookslm-picker-host + ai-picker +
  .bookslm-header button obtiennent flex-shrink:0 + z-index:1 pour
  éviter que les selects compressent ou masquent les boutons
  header (Nouvelle conversation / Exporter / Plein écran / Fermer)
- Bug 4 (theme picker): ai.js — var(--bg-tertiary, transparent) →
  var(--surface), var(--border-color) → var(--border) sur tous les
  selects, menus et createSeparator. Plus de variables inexistantes.

Tests: pytest 504 passed, frontend unit 7/7, validate-imports 30 modules
204 exports, pane-manager 9/9, ruff All checks passed.

frontend/js/ai.js

@@ -68,15 +68,17 @@ async function _buildPickerUI() {
   const wrap = document.createElement('div');
   wrap.className = 'ai-picker';
   Object.assign(wrap.style, {
-    display: 'inline-flex',
-    alignItems: 'center',
-    gap: '4px',
-    marginLeft: '8px',
-    paddingLeft: '8px',
-    borderLeft: '1px solid var(--border-color)',
-    fontSize: '0.7rem',
-    color: 'var(--text-muted)',
-  });
+      display: 'inline-flex',
+      alignItems: 'center',
+      gap: '4px',
+      marginLeft: '8px',
+      paddingLeft: '8px',
+      borderLeft: '1px solid var(--border)',
+      fontSize: '0.7rem',
+      color: 'var(--text-muted)',
+      flexShrink: '0',
+      zIndex: '1',
+    });
 
   // Provider select
   const providerLabel = document.createElement('span');
@@ -86,14 +88,14 @@ async function _buildPickerUI() {
   const providerSelect = document.createElement('select');
   providerSelect.className = 'ai-picker-select';
   Object.assign(providerSelect.style, {
-    fontSize: '0.7rem',
-    background: 'var(--bg-tertiary, transparent)',
-    color: 'var(--text-primary)',
-    border: '1px solid var(--border-color)',
-    borderRadius: '4px',
-    padding: '2px 4px',
-    cursor: 'pointer',
-  });
+      fontSize: '0.7rem',
+      background: 'var(--surface)',
+      color: 'var(--text-primary)',
+      border: '1px solid var(--border)',
+      borderRadius: '4px',
+      padding: '2px 4px',
+      cursor: 'pointer',
+    });
 
   const defaultOpt = document.createElement('option');
   defaultOpt.value = '';
@@ -111,16 +113,16 @@ async function _buildPickerUI() {
   const modelSelect = document.createElement('select');
   modelSelect.className = 'ai-picker-model';
   Object.assign(modelSelect.style, {
-    fontSize: '0.7rem',
-    background: 'var(--bg-tertiary, transparent)',
-    color: 'var(--text-primary)',
-    border: '1px solid var(--border-color)',
-    borderRadius: '4px',
-    padding: '2px 4px',
-    cursor: 'pointer',
-    minWidth: '120px',
-    maxWidth: '220px',
-  });
+      fontSize: '0.7rem',
+      background: 'var(--surface)',
+      color: 'var(--text-primary)',
+      border: '1px solid var(--border)',
+      borderRadius: '4px',
+      padding: '2px 4px',
+      cursor: 'pointer',
+      minWidth: '120px',
+      maxWidth: '220px',
+    });
   const placeholderOpt = document.createElement('option');
   placeholderOpt.value = '';
   placeholderOpt.textContent = t('ai.model_default');
@@ -244,12 +246,12 @@ function createMenu(items, parentEl) {
   const menuLeft = rect.left;
 
   Object.assign(menu.style, {
-    position: 'fixed',
-    top: menuTop + 'px',
-    left: menuLeft + 'px',
-    background: 'var(--bg-primary)',
-    border: '1px solid var(--border-color)',
-    borderRadius: '6px',
+      position: 'fixed',
+      top: menuTop + 'px',
+      left: menuLeft + 'px',
+      background: 'var(--bg-primary)',
+      border: '1px solid var(--border)',
+      borderRadius: '6px',
     padding: '4px 0',
     minWidth: '200px',
     maxHeight: '60vh',
@@ -336,12 +338,12 @@ function createSubMenu(items, parentEl) {
   const menu = document.createElement('div');
   menu.className = 'ai-submenu';
   Object.assign(menu.style, {
-    position: 'absolute',
-    left: '100%',
-    top: '0',
-    background: 'var(--bg-primary)',
-    border: '1px solid var(--border-color)',
-    borderRadius: '6px',
+      position: 'absolute',
+      left: '100%',
+      top: '0',
+      background: 'var(--bg-primary)',
+      border: '1px solid var(--border)',
+      borderRadius: '6px',
     padding: '4px 0',
     minWidth: '180px',
     zIndex: '101',
@@ -384,7 +386,7 @@ export async function createAIToolbar(container, getEditorView) {
   
   if (!aiConfigured) {
     const hint = document.createElement('div');
-    hint.style.cssText = 'padding:6px 12px;font-size:0.7rem;color:var(--text-muted);border-bottom:1px solid var(--border-color)';
+    hint.style.cssText = 'padding:6px 12px;font-size:0.7rem;color:var(--text-muted);border-bottom:1px solid var(--border)';
     hint.textContent = t('ai.not_configured');
     container.appendChild(hint);
     return;
@@ -397,7 +399,7 @@ export async function createAIToolbar(container, getEditorView) {
     alignItems: 'center',
     gap: '2px',
     padding: '4px 8px',
-    borderBottom: '1px solid var(--border-color)',
+    borderBottom: '1px solid var(--border)',
     background: 'var(--bg-secondary)',
     flexWrap: 'wrap',
     position: 'sticky',
@@ -623,7 +625,7 @@ function createDropdownBtn(text, items, tooltip = '') {
 
 function createSeparator() {
   const sep = document.createElement('span');
-  sep.style.cssText = 'width:1px;height:16px;background:var(--border-color);margin:0 2px';
+  sep.style.cssText = 'width:1px;height:16px;background:var(--border);margin:0 2px';
   return sep;
 }
 

frontend/js/bookslm.js

@@ -311,8 +311,16 @@ class BooksLM {
         body: JSON.stringify({
           vault: this._vault,
           directory: this._directory,
-          messages: this._messages.slice(0, -1), // exclude empty assistant
-          context_files: this._contextFiles.map(f => f.path || f),
+          // The backend expects `message` + `conversation_history`,
+          // not a generic `messages` array. Convert before sending.
+          message: this._messages.length
+            ? this._messages[this._messages.length - 1].content
+            : '',
+          conversation_history: this._messages
+            .slice(0, -1)
+            .filter((m) => m.content && m.content.trim())
+            .map((m) => ({ role: m.role, content: m.content })),
+          context_files: this._contextFiles.map((f) => f.path || f),
           provider,
           model,
         }),