feat: permission mode info tooltip on hover

Show a brief description of the current permission mode (Plan/Edit/Full
Auto) when hovering the permission bar. Also sets a native title tooltip
with the same text.

Author: abose

src/nls/root/strings.js

@@ -1929,6 +1929,9 @@ define({
     "AI_CHAT_MODE_PLAN": "Plan Mode",
     "AI_CHAT_MODE_EDIT": "Edit Mode",
     "AI_CHAT_MODE_FULL_AUTO": "Full Auto",
+    "AI_CHAT_MODE_INFO_PLAN": "AI will propose a plan before making changes",
+    "AI_CHAT_MODE_INFO_EDIT": "AI can edit files. Shell commands need approval",
+    "AI_CHAT_MODE_INFO_FULL_AUTO": "AI can edit files and run commands without approval",
     "AI_CHAT_BASH_CONFIRM_TITLE": "Allow command?",
     "AI_CHAT_BASH_ALLOW": "Allow",
     "AI_CHAT_BASH_DENY": "Deny",

src/styles/Extn-AIChatPanel.less

@@ -1747,6 +1747,22 @@
             color: @project-panel-text-2;
             line-height: 1;
         }
+
+        .ai-permission-info {
+            display: none;
+            margin-left: auto;
+            font-size: 11px;
+            line-height: 1;
+            pointer-events: none;
+            white-space: nowrap;
+            overflow: hidden;
+            text-overflow: ellipsis;
+            color: @project-panel-text-2;
+        }
+
+        &:hover .ai-permission-info {
+            display: inline;
+        }
     }
 
     .ai-chat-context-bar {