chore(lint): unify formatting on golangci-lint fmt (gofumpt), uncap issue reporting, fix gofumpt drift

- make format 现在与 code-check 使用同一格式化器（golangci-lint fmt），消除 goimports -local 与 gofumpt 的格式拉锯
- .golangci.yml 关闭默认 50/3 截断，完整上报所有问题（只增强不弱化）
- 全库 gofumpt 规范化（203 files, 纯格式无行为变更）

backend/core/context.go

@@ -4,13 +4,12 @@
 package core
 
 import (
+	"Wavelet/core/extpoints"
 	"context"
 	"errors"
 	"fmt"
 	"sync"
 	"time"
-
-	"Wavelet/core/extpoints"
 )
 
 // Context is the central micro-kernel service bus and runtime lifecycle container.
@@ -103,7 +102,7 @@ func (c *Context) GoContext() context.Context {
 }
 
 // Set stores an arbitrary key-value pair in this Context's local storage.
-func (c *Context) Set(key any, val any) {
+func (c *Context) Set(key, val any) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	if c.values == nil {