feat: unified hook notifier, agent auto-detection, terminal transition UI

- Add hooks/notify.ps1 as single hook handler for all events
- Refactor settings.local.json to use notify.ps1 instead of inline PS
- Add Notification hook, auto-detect agent from session_id/transcript
- Rename agent 'main' to 'claude' across server routes and terminal
- Add loading overlay and error state for terminal switching transitions
- Add transitionError ref to useTranscriptDebug composable

frontend/src/components/FloatingTranscriptDebug.vue

@@ -28,6 +28,8 @@ const {
   selectedSessionId,
   conversation,
   loading,
+  transitioning,
+  transitionError,
   error,
   isRealtime,
   processing,
@@ -702,6 +704,22 @@ onBeforeUnmount(() => {
           <div class="content">
             <AquaticBackground />
             <div class="readability-overlay" :style="{ background: `rgba(0, 0, 0, ${overlayOpacity})` }" />
+            <Transition name="terminal-loading">
+              <div v-if="transitioning" class="terminal-loading-overlay">
+                <div class="terminal-loading-spinner" />
+              </div>
+            </Transition>
+            <Transition name="terminal-loading">
+              <div v-if="transitionError" class="terminal-error-overlay" @click="transitionError = null">
+                <div class="terminal-error-content">
+                  <svg width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="#f87171" stroke-width="2">
+                    <circle cx="12" cy="12" r="10"/><line x1="12" y1="8" x2="12" y2="12"/><line x1="12" y1="16" x2="12.01" y2="16"/>
+                  </svg>
+                  <span class="terminal-error-msg">{{ transitionError }}</span>
+                  <span class="terminal-error-hint">Click to dismiss</span>
+                </div>
+              </div>
+            </Transition>
             <ChatContainer
               ref="chatRef"
               v-if="conversation"
@@ -1180,6 +1198,73 @@ onBeforeUnmount(() => {
   opacity: 1;
 }
 
+/* ── Terminal switching loading overlay ── */
+.terminal-loading-overlay {
+  position: absolute;
+  inset: 0;
+  z-index: 5;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: rgba(0, 0, 0, 0.35);
+  backdrop-filter: blur(4px);
+}
+
+.terminal-loading-spinner {
+  width: 28px;
+  height: 28px;
+  border: 2.5px solid rgba(255, 255, 255, 0.15);
+  border-top-color: rgba(255, 255, 255, 0.7);
+  border-radius: 50%;
+  animation: tl-spin 0.7s linear infinite;
+}
+
+@keyframes tl-spin {
+  to { transform: rotate(360deg); }
+}
+
+.terminal-error-overlay {
+  position: absolute;
+  inset: 0;
+  z-index: 5;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: rgba(0, 0, 0, 0.45);
+  backdrop-filter: blur(6px);
+  cursor: pointer;
+}
+
+.terminal-error-content {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 0.6rem;
+  max-width: 80%;
+  padding: 1.2rem 1.5rem;
+  background: rgba(30, 30, 30, 0.85);
+  border: 1px solid rgba(248, 113, 113, 0.3);
+  border-radius: 10px;
+}
+
+.terminal-error-msg {
+  font-size: 12px;
+  color: #fca5a5;
+  text-align: center;
+  line-height: 1.4;
+  word-break: break-word;
+}
+
+.terminal-error-hint {
+  font-size: 10px;
+  color: rgba(255, 255, 255, 0.35);
+}
+
+.terminal-loading-enter-active { transition: opacity 0.15s ease; }
+.terminal-loading-leave-active { transition: opacity 0.25s ease; }
+.terminal-loading-enter-from,
+.terminal-loading-leave-to { opacity: 0; }
+
 /* Override ChatContainer backgrounds: glass-transparent */
 .content :deep(.chat-container) {
   background: transparent !important;