canvas/{Details,Config,Activity}Tab: button hover sweep across 6 buttons

Six button fixes — same trap patterns shipped on every other tab:

DetailsTab:
- Save button: bg-accent-strong hover:bg-accent (LIGHTER on white text,
  AA drop) → bg-accent hover:bg-accent-strong + focus-visible ring.
- Confirm Delete: bg-red-600 hover:bg-red-500 (LIGHTER on white text,
  AA drop) → bg-red-700 + focus-visible danger ring.
- Cancel: bg-surface-card hover:bg-surface-card (no-op) →
  surface-elevated.

ConfigTab:
- 2× Save buttons: same accent-LIGHTER trap → flipped + focus rings.
- Cancel: same no-op → surface-elevated.

ActivityTab:
- Refresh: same no-op → surface-elevated + focus-visible ring.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

canvas/src/components/tabs/ActivityTab.tsx

@@ -110,8 +110,11 @@ export function ActivityTab({ workspaceId }: Props) {
               Full Trace
             </button>
             <button
+              type="button"
               onClick={loadActivities}
-              className="px-2 py-1 bg-surface-card hover:bg-surface-card text-[11px] rounded text-ink-mid"
+              // hover:bg-surface-card on top of itself was a no-op;
+              // lift to surface-elevated + focus-visible ring.
+              className="px-2 py-1 bg-surface-card hover:bg-surface-elevated hover:text-ink text-[11px] rounded text-ink-mid transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-accent/50"
             >
               Refresh
             </button>

canvas/src/components/tabs/ConfigTab.tsx

@@ -65,11 +65,11 @@ function AgentCardSection({ workspaceId }: { workspaceId: string }) {
           {error && <div className="px-2 py-1 bg-red-900/30 border border-red-800 rounded text-[10px] text-bad">{error}</div>}
           <div className="flex gap-2">
             <button type="button" onClick={handleSave} disabled={saving}
-              className="px-2 py-1 bg-accent-strong hover:bg-accent text-[10px] rounded text-white disabled:opacity-50">
+              className="px-2 py-1 bg-accent hover:bg-accent-strong text-[10px] rounded text-white disabled:opacity-50 transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-accent/60 focus-visible:ring-offset-1 focus-visible:ring-offset-surface">
               {saving ? "Saving..." : "Save"}
             </button>
             <button type="button" onClick={() => setEditing(false)}
-              className="px-2 py-1 bg-surface-card hover:bg-surface-card text-[10px] rounded text-ink-mid">Cancel</button>
+              className="px-2 py-1 bg-surface-card hover:bg-surface-elevated hover:text-ink text-[10px] rounded text-ink-mid transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-accent/40 focus-visible:ring-offset-1 focus-visible:ring-offset-surface">Cancel</button>
           </div>
         </div>
       ) : (
@@ -956,7 +956,8 @@ export function ConfigTab({ workspaceId }: Props) {
           type="button"
           onClick={() => handleSave(true)}
           disabled={!isDirty || saving}
-          className="px-3 py-1.5 bg-accent-strong hover:bg-accent text-xs rounded text-white disabled:opacity-30 transition-colors"
+          // Same accent-LIGHTER fix shipped on every other tab.
+          className="px-3 py-1.5 bg-accent hover:bg-accent-strong text-xs rounded text-white disabled:opacity-30 transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-accent/60 focus-visible:ring-offset-1 focus-visible:ring-offset-surface"
         >
           {saving ? "Restarting..." : "Save & Restart"}
         </button>

canvas/src/components/tabs/DetailsTab.tsx

@@ -166,7 +166,10 @@ export function DetailsTab({ workspaceId, data }: Props) {
                 type="button"
                 onClick={handleSave}
                 disabled={saving}
-                className="px-3 py-1 bg-accent-strong hover:bg-accent text-xs rounded text-white disabled:opacity-50"
+                // Was bg-accent-strong hover:bg-accent — accent is the
+                // LIGHTER variant; flipped + focus-visible ring (same
+                // trap fix shipped on every other tab).
+                className="px-3 py-1 bg-accent hover:bg-accent-strong text-xs rounded text-white disabled:opacity-50 transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-accent/60 focus-visible:ring-offset-1 focus-visible:ring-offset-surface"
               >
                 {saving ? "Saving..." : "Save"}
               </button>
@@ -322,7 +325,10 @@ export function DetailsTab({ workspaceId, data }: Props) {
               <button
                 type="button"
                 onClick={handleDelete}
-                className="px-3 py-1 bg-red-600 hover:bg-red-500 text-xs rounded text-white"
+                // hover:bg-red-500 LIGHTER on white text drops AA;
+                // flipped to bg-red-700 + focus-visible danger ring,
+                // matching the ConfirmDialog/DeleteCascade pattern.
+                className="px-3 py-1 bg-red-600 hover:bg-red-700 text-xs rounded text-white transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-red-500/60 focus-visible:ring-offset-1 focus-visible:ring-offset-surface"
               >
                 Confirm Delete
               </button>
@@ -334,7 +340,9 @@ export function DetailsTab({ workspaceId, data }: Props) {
                   // Return focus to the trigger so keyboard users aren't stranded
                   deleteButtonRef.current?.focus();
                 }}
-                className="px-3 py-1 bg-surface-card hover:bg-surface-card text-xs rounded text-ink-mid"
+                // Was hover:bg-surface-card on top of itself (no-op);
+                // lift to surface-elevated.
+                className="px-3 py-1 bg-surface-card hover:bg-surface-elevated hover:text-ink text-xs rounded text-ink-mid transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-accent/40 focus-visible:ring-offset-1 focus-visible:ring-offset-surface"
               >
                 Cancel
               </button>