refactor: consolidate AvailableVariables component and enhance variable display logic across dialogs

- Moved `AvailableVariables` to shared directory.
- Updated dialogs to use shared `AvailableVariables` component.
- Enhanced inline expressions and processors dialog with better variable display.

studio/frontend/src/features/canvas-lab/components/inline/inline-expression.tsx

@@ -1,3 +1,4 @@
+import { Badge } from "@/components/ui/badge";
 import { Input } from "@/components/ui/input";
 import {
   Select,
@@ -7,7 +8,9 @@ import {
   SelectValue,
 } from "@/components/ui/select";
 import type { ReactElement } from "react";
+import { useCanvasLabStore } from "../../stores/canvas-lab";
 import type { ExpressionConfig, ExpressionDtype } from "../../types";
+import { getAvailableVariables } from "../../utils/variables";
 import { InlineField } from "./inline-field";
 
 type InlineExpressionProps = {
@@ -21,35 +24,56 @@ export function InlineExpression({
   config,
   onUpdate,
 }: InlineExpressionProps): ReactElement {
+  const configs = useCanvasLabStore((state) => state.configs);
+  const vars = getAvailableVariables(configs, config.id);
+
   return (
-    <div className="grid gap-3 sm:grid-cols-[130px_1fr]">
-      <InlineField label="Output type">
-        <Select
-          value={config.dtype}
-          onValueChange={(value) =>
-            onUpdate({ dtype: value as ExpressionDtype })
-          }
-        >
-          <SelectTrigger className="nodrag h-8 w-full text-xs">
-            <SelectValue placeholder="dtype" />
-          </SelectTrigger>
-          <SelectContent>
-            {DTYPE_OPTIONS.map((dtype) => (
-              <SelectItem key={dtype} value={dtype}>
-                {dtype}
-              </SelectItem>
+    <div className="space-y-3">
+      <div className="grid gap-3 sm:grid-cols-[130px_1fr]">
+        <InlineField label="Output type">
+          <Select
+            value={config.dtype}
+            onValueChange={(value) =>
+              onUpdate({ dtype: value as ExpressionDtype })
+            }
+          >
+            <SelectTrigger className="nodrag h-8 w-full text-xs">
+              <SelectValue placeholder="dtype" />
+            </SelectTrigger>
+            <SelectContent>
+              {DTYPE_OPTIONS.map((dtype) => (
+                <SelectItem key={dtype} value={dtype}>
+                  {dtype}
+                </SelectItem>
+              ))}
+            </SelectContent>
+          </Select>
+        </InlineField>
+        <InlineField label="Expression">
+          <Input
+            className="nodrag h-8 w-full text-xs"
+            placeholder="{{ column_name }}"
+            value={config.expr}
+            onChange={(event) => onUpdate({ expr: event.target.value })}
+          />
+        </InlineField>
+      </div>
+      {vars.length > 0 && (
+        <div className="space-y-1">
+          <p className="text-[10px] font-medium text-muted-foreground">Available references</p>
+          <div className="flex flex-wrap gap-1">
+            {vars.map((v) => (
+              <Badge
+                key={v}
+                variant="secondary"
+                className="corner-squircle h-4 px-1.5 font-mono text-[10px]"
+              >
+                {v}
+              </Badge>
             ))}
-          </SelectContent>
-        </Select>
-      </InlineField>
-      <InlineField label="Expression">
-        <Input
-          className="nodrag h-8 w-full text-xs"
-          placeholder="{{ column_name }}"
-          value={config.expr}
-          onChange={(event) => onUpdate({ expr: event.target.value })}
-        />
-      </InlineField>
+          </div>
+        </div>
+      )}
     </div>
   );
 }

studio/frontend/src/features/canvas-lab/dialogs/expression/expression-dialog.tsx

@@ -8,6 +8,7 @@ import {
 import { Textarea } from "@/components/ui/textarea";
 import type { ReactElement } from "react";
 import type { ExpressionConfig, ExpressionDtype } from "../../types";
+import { AvailableVariables } from "../shared/available-variables";
 import { NameField } from "../shared/name-field";
 
 const DTYPE_OPTIONS: ExpressionDtype[] = ["str", "int", "float", "bool"];
@@ -31,6 +32,7 @@ export function ExpressionDialog({
   };
   return (
     <div className="space-y-4">
+      <AvailableVariables configId={config.id} />
       <NameField
         value={config.name}
         onChange={(value) => onUpdate({ name: value })}

studio/frontend/src/features/canvas-lab/dialogs/llm/llm-dialog.tsx

@@ -17,7 +17,7 @@ import {
 import { Textarea } from "@/components/ui/textarea";
 import { type ReactElement, useEffect, useRef, useState } from "react";
 import type { LlmConfig, Score } from "../../types";
-import { AvailableVariables } from "./available-variables";
+import { AvailableVariables } from "../shared/available-variables";
 import { NameField } from "../shared/name-field";
 
 const CODE_LANG_OPTIONS = [

studio/frontend/src/features/canvas-lab/dialogs/processors-dialog.tsx

@@ -7,6 +7,7 @@ import { VisuallyHidden } from "radix-ui";
 import { type ReactElement, useMemo } from "react";
 import type { CanvasProcessorConfig } from "../types";
 import { buildDefaultSchemaTransform } from "../utils/processors";
+import { AvailableVariables } from "./shared/available-variables";
 type ProcessorsDialogProps = {
   open: boolean;
   onOpenChange: (open: boolean) => void;
@@ -72,7 +73,7 @@ export function ProcessorsDialog({
           <DialogTitle>Processors</DialogTitle>
         </VisuallyHidden.Root>
         <div className="space-y-4">
-          <div className="flex items-center justify-between gap-3 rounded-2xl border border-border/60 px-3 py-2">
+          <div className="flex items-center justify-between gap-3 corner-squircle rounded-2xl border border-border/60 px-3 py-2">
             <div>
               <p className="text-sm font-semibold">Schema transform</p>
               <p className="text-xs text-muted-foreground">
@@ -87,6 +88,7 @@ export function ProcessorsDialog({
 
           {schemaProcessor && (
             <div className="space-y-3">
+              <AvailableVariables configId="" />
               <div className="grid gap-2">
                 <label
                   className="text-xs font-semibold uppercase text-muted-foreground"

studio/frontend/src/features/canvas-lab/dialogs/shared/available-variables.tsx

@@ -1,36 +1,36 @@
-import { Badge } from "@/components/ui/badge";
-import type { ReactElement } from "react";
-import { useCanvasLabStore } from "../../stores/canvas-lab";
-import { getAvailableVariables } from "../../utils/variables";
-
-type AvailableVariablesProps = {
-  configId: string;
-};
-
-export function AvailableVariables({
-  configId,
-}: AvailableVariablesProps): ReactElement | null {
-  const configs = useCanvasLabStore((state) => state.configs);
-  const vars = getAvailableVariables(configs, configId);
-
-  if (vars.length === 0) return null;
-
-  return (
-    <div className="corner-squircle rounded-2xl border border-border/60 px-3 py-2">
-      <p className="mb-2 text-xs font-semibold uppercase text-muted-foreground">
-        Available variables
-      </p>
-      <div className="flex flex-wrap gap-1.5">
-        {vars.map((v) => (
-          <Badge
-            key={v}
-            variant="secondary"
-            className="corner-squircle font-mono text-[11px]"
-          >
-            {`{{ ${v} }}`}
-          </Badge>
-        ))}
-      </div>
-    </div>
-  );
-}
+import { Badge } from "@/components/ui/badge";
+import type { ReactElement } from "react";
+import { useCanvasLabStore } from "../../stores/canvas-lab";
+import { getAvailableVariables } from "../../utils/variables";
+
+type AvailableVariablesProps = {
+  configId: string;
+};
+
+export function AvailableVariables({
+  configId,
+}: AvailableVariablesProps): ReactElement | null {
+  const configs = useCanvasLabStore((state) => state.configs);
+  const vars = getAvailableVariables(configs, configId);
+
+  if (vars.length === 0) return null;
+
+  return (
+    <div className="corner-squircle rounded-2xl border border-border/60 px-3 py-2">
+      <p className="mb-2 text-xs font-semibold uppercase text-muted-foreground">
+        Available references
+      </p>
+      <div className="flex flex-wrap gap-1.5">
+        {vars.map((v) => (
+          <Badge
+            key={v}
+            variant="secondary"
+            className="corner-squircle font-mono text-[11px]"
+          >
+            {`{{ ${v} }}`}
+          </Badge>
+        ))}
+      </div>
+    </div>
+  );
+}