Remove remaining animations and fix file browser issues

- Swap file picker and settings buttons in session header (settings now at the end)
- Disable all button transitions in session view with body.in-session-view
- Disable modal backdrop fade-in animation (0.3s) in session view
- Fix file browser briefly showing then going dark by preventing event bubbling
- Add stopPropagation to file browser button click to prevent duplicate modals

The session detail page should now have zero animations when toggling sidebar
or opening modals.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

web/src/client/components/session-view/session-header.ts

@@ -157,9 +157,15 @@ export class SessionHeader extends LitElement {
           </div>
         </div>
         <div class="flex items-center gap-2 text-xs flex-shrink-0 ml-2 relative">
+          <notification-status
+            @open-settings=${() => this.onOpenSettings?.()}
+          ></notification-status>
           <button
             class="bg-dark-bg-elevated border border-dark-border rounded-lg p-2 font-mono text-dark-text-muted transition-all duration-200 hover:text-accent-primary hover:bg-dark-surface-hover hover:border-accent-primary hover:shadow-sm flex-shrink-0"
-            @click=${() => this.onOpenFileBrowser?.()}
+            @click=${(e: Event) => {
+              e.stopPropagation();
+              this.onOpenFileBrowser?.();
+            }}
             title="Browse Files (⌘O)"
             data-testid="file-browser-button"
           >
@@ -169,9 +175,6 @@ export class SessionHeader extends LitElement {
               />
             </svg>
           </button>
-          <notification-status
-            @open-settings=${() => this.onOpenSettings?.()}
-          ></notification-status>
           <button
             class="bg-dark-bg-elevated border border-dark-border rounded-lg p-2 font-mono text-dark-text-muted transition-all duration-200 hover:text-accent-primary hover:bg-dark-surface-hover hover:border-accent-primary hover:shadow-sm flex-shrink-0"
             @click=${() => this.onScreenshare?.()}

web/src/client/styles.css

@@ -541,6 +541,24 @@ body.in-session-view .space-y-2 > div {
   animation-delay: 0s !important;
 }
 
+/* Disable all transitions on buttons in session view */
+body.in-session-view button {
+  transition: none !important;
+}
+
+/* Disable transitions on all interactive elements in session view */
+body.in-session-view .transition-all,
+body.in-session-view .transition-colors,
+body.in-session-view .transition-opacity,
+body.in-session-view .transition-transform {
+  transition: none !important;
+}
+
+/* Disable modal backdrop animation in session view */
+body.in-session-view .modal-backdrop {
+  animation: none !important;
+}
+
 /* Stagger animation when showing exited sessions */
 body.sessions-showing .session-flex-responsive > session-card:nth-child(1) {
   animation-delay: 0s;