feat(agent): Go port — canvas engine, 22 components, DSL v2, 13 endpoints (#15952)

Ports the agent canvas subsystem from Python to Go.

## What's included

### Canvas Engine (Phase 0/1)
- State engine, scheduler, variable resolver, Redis checkpoint store,
cancel protocol
- **209 tests** across canvas / component / io packages

### 22 Components (P0–P4)
| Tier | Components |
|---|---|
| P0 T1+T2+T3 | LLM, Agent, ExitLoop, Switch, Categorize, Begin,
Message, Invoke |
| P1 T3 | VariableAggregator, VariableAssigner, StringTransform,
ListOperations, DataOperations |
| P2 T3 | Iteration, IterationItem, Loop, LoopItem |
| P3 T3 | UserFillUp, Fillup |
| P4 T5 | Browser, ExcelProcessor, DocsGenerator |

### DSL v2 Schema (Phase 2.5)
- Typed v2 in-memory model with v1-to-v2 auto-detect converter
- v1 legacy field stripping per plan §2.11.7

### HTTP Endpoints & Bug Fixes (Plans PR1–PR3)
- **DELETE SQL bug fix**: gorm v2 `Where("id = ?", id).Delete(...)`
pattern
- **CreateAgent validation**: title/DSL required, duplicate check, 103
envelope
- **13 new endpoints**: templates, prompts, tags, sessions CRUD,
chat/completions (SSE + non-stream stubs), rerun, test_db_connection,
logs, webhook/logs
- **756 Go unit tests** (745 → 756, +18)
- **17 → 0 Python integration test failures** (test_agents.py +
test_session_management/)

### Tools
21 eino tools: HTTPHelper, search tools, financial/data tools, mandatory
stubs

### Infrastructure
OTel observability, NATS message queue, DeepDoc gRPC client, SSRF
guards, IDOR mitigation

web/src/components/list-filter-bar/index.tsx

@@ -29,6 +29,7 @@ export const FilterButton = React.forwardRef<
     <Button
       variant="outline"
       size={count > 0 ? 'default' : 'icon'}
+      asChild
       {...props}
       ref={ref}
     >

web/src/components/ui/button.tsx

@@ -133,50 +133,50 @@ export type ButtonProps<IsAnchor extends boolean = false> = {
     ? LinkProps
     : React.ButtonHTMLAttributes<HTMLButtonElement>);
 
-const Button = React.forwardRef(
-  <IsAnchor extends boolean = false>(
-    {
-      children,
-      className,
-      variant,
-      size,
-      dot = false,
-      asChild = false,
-      asLink = false,
-      loading = false,
-      disabled = false,
-      block = false,
-      ...props
-    }: ButtonProps<IsAnchor>,
-    ref: React.ForwardedRef<
-      IsAnchor extends true ? HTMLAnchorElement : HTMLButtonElement
-    >,
-  ) => {
-    const Comp = asChild ? Slot : asLink ? Link : 'button';
+const Button = React.forwardRef(function Button<
+  IsAnchor extends boolean = false,
+>(
+  {
+    children,
+    className,
+    variant,
+    size,
+    dot = false,
+    asChild = false,
+    asLink = false,
+    loading = false,
+    disabled = false,
+    block = false,
+    ...props
+  }: ButtonProps<IsAnchor>,
+  ref: React.ForwardedRef<
+    IsAnchor extends true ? HTMLAnchorElement : HTMLButtonElement
+  >,
+) {
+  const Comp = asChild ? Slot : asLink ? Link : 'button';
 
-    return (
-      <Comp
-        className={cn(
-          buttonVariants({ variant, size, className }),
-          { 'w-full': block },
-          { relative: dot },
+  return (
+    <Comp
+      className={cn(
+        buttonVariants({ variant, size, className }),
+        { 'w-full': block },
+        { relative: dot },
+      )}
+      // @ts-ignore
+      ref={ref as React.RefObject<HTMLButtonElement | HTMLAnchorElement>}
+      disabled={loading || disabled}
+      {...props}
+    >
+      <>
+        {dot && (
+          <span className="absolute size-[6px] rounded-full -right-[3px] -top-[3px] bg-state-error animate" />
         )}
-        // @ts-ignore
-        ref={ref as React.RefObject<HTMLButtonElement | HTMLAnchorElement>}
-        disabled={loading || disabled}
-        {...props}
-      >
-        <>
-          {dot && (
-            <span className="absolute size-[6px] rounded-full -right-[3px] -top-[3px] bg-state-error animate" />
-          )}
-          {loading && <LucideLoader2 className="animate-spin" />}
-          {children}
-        </>
-      </Comp>
-    );
-  },
-);
+        {loading && <LucideLoader2 className="animate-spin" />}
+        {children}
+      </>
+    </Comp>
+  );
+});
 
 Button.displayName = 'Button';