fix(filters): group mode reads AND/OR, connective labels toggle it (user report)

The ALL/ANY pills required mapping ALL→AND, ANY→OR that nobody should
have to learn. The pills now say AND / OR directly (wire values stay
all|any — server contract untouched), and the AND/OR text between
sibling rules became a clickable toggle for its parent group, so the
switch lives exactly where you're looking.

web/static/input.css

@@ -2063,3 +2063,20 @@
     border-left: 2px solid var(--border);
     padding-left: 0.6rem;
   }
+  .fb-connective-btn {
+    font-size: 0.65rem;
+    font-weight: 700;
+    letter-spacing: 0.05em;
+    color: var(--text-secondary);
+    min-width: 1.9rem;
+    padding: 0.1rem 0.3rem;
+    border: 1px dashed var(--border);
+    border-radius: 0.4rem;
+    background-color: transparent;
+    cursor: pointer;
+    text-align: center;
+  }
+  .fb-connective-btn:hover {
+    color: var(--accent);
+    border-color: color-mix(in srgb, var(--accent) 45%, var(--border));
+  }