fix(goctl): recurse into inline struct in IsTagMember

[014-code]

概述

Fix #4800: goctl api ts
generates a spurious headers parameter on TypeScript request functions
when the request type contains an inline (anonymous-embedded) struct.

Root cause: Member.IsTagMember unconditionally returned true for any
tag key on an inline member, instead of recursing into the members of
the referenced struct. That made tsgen.hasRequestHeader (which calls
GetTagMembers("header")) treat every inline struct as having
header-tagged fields and emit a headers parameter even when the
interface defines no header field at all.

变更内容

• tools/goctl/api/spec/fn.go
  • IsTagMember now first checks the member's own tags.
  • For inline members, it recurses into the DefineStruct or
    NestedStruct referenced by Type.Members and only returns true
    when a child actually carries the requested tag.
• tools/goctl/api/spec/fn_test.go (new)
  • Covers non-inline members, inline DefineStruct / NestedStruct
    with and without matching child tags, nested inline structs, and
    the exact When generating TypeScript code, there is an additional headers parameter #4800 scenario via DefineStruct.GetTagMembers("header").

测试

• Unit: go test ./tools/goctl/api/spec/ -v
  • 10 new subtests + 1 regression test, all PASS alongside the
    pre-existing 4 tests in the package.
• End-to-end: reproduced the minimal .api from When generating TypeScript code, there is an additional headers parameter #4800 (an inline
  Pagination struct with only json tags) with
  go run ./tools/goctl/goctl.go api ts -api demo.api -dir out.
  The generated queryUserList function now takes only req — the
  spurious headers parameter is gone.

是否有破坏性变更？

否. The new behavior of IsTagMember is consistent with its existing
docstring ("returns true if the member contains the given tag"); an
inline member that carries no matching tag should not have reported
true before this fix either. No real consumer relies on the old
always-true behavior — it was the source of the bug itself.

Fixes #4800