[kernel] Prevent duplicate defunct enqueue for deleted threads.

[Rbb666]

拉取/合并请求描述：(PR description)

[

为什么提交这份PR (why to submit this PR)

RT-Thread 线程正常退出时会通过 _thread_exit() 进入 defunct 队列，随后由 idle/system defunct 线程完成资源回收。但应用层仍可能误调用 rt_thread_delete() 或 rt_thread_detach()，导致同一个线程被重复加入 defunct 队列，存在链表破坏、重复销毁和资源回收异常的风险。

这类误用在实际 APP 中比较容易出现，例如线程主循环自然退出后，外部管理逻辑又再次删除线程，因此内核侧需要提供保护，避免应用层错误使用直接破坏线程生命周期管理。

你的解决方案是什么 (what is your solution)

为线程调度上下文增加 sched_flag_defunct 标志，用于记录线程是否已经进入 defunct 队列，并在 rt_sched_thread_init_ctx() 中初始化。
新增 _thread_mark_defunct()，通过线程自身的 spinlock 保护该标志的检查和设置，确保 _thread_exit()、rt_thread_delete()、rt_thread_detach() 只有第一次能将线程加入 defunct 队列。后续重复 delete/detach 会返回错误，不再重复执行 mutex detach 和 defunct enqueue。
同时补充 core.thread_tc 回归测试，覆盖：

• 动态线程重复 rt_thread_delete()。
• 动态线程主循环自然退出触发 _thread_exit() 后，再调用 rt_thread_delete()。
• 静态线程重复 rt_thread_detach()。
• 静态线程自然退出触发 _thread_exit() 后，再调用 rt_thread_detach()。

请提供验证的bsp和config (provide the config and bsp)

• BSP:

• .config:

• action:

]

当前拉取/合并请求的状态 Intent for your PR

必须选择一项 Choose one (Mandatory):

• 本拉取/合并请求是一个草稿版本 This PR is for a code-review and is intended to get feedback
• 本拉取/合并请求是一个成熟版本 This PR is mature, and ready to be integrated into the repo

代码质量 Code Quality：

我在这个拉取/合并请求中已经考虑了 As part of this pull request, I've considered the following:

• 已经仔细查看过代码改动的对比 Already check the difference between PR and old code
• 代码风格正确，包括缩进空格，命名及其他风格 Style guide is adhered to, including spacing, naming and other styles
• 没有垃圾代码，代码尽量精简，不包含#if 0代码，不包含已经被注释了的代码 All redundant code is removed and cleaned up
• 所有变更均有原因及合理的，并且不会影响到其他软件组件代码或BSP All modifications are justified and not affect other components or BSP
• 对难懂代码均提供对应的注释 I've commented appropriately where code is tricky
• 代码是高质量的 Code in this PR is of high quality
• 已经使用formatting 等源码格式化工具确保格式符合RT-Thread代码规范 This PR complies with RT-Thread code specification
• 如果是新增bsp, 已经添加ci检查到.github/ALL_BSP_COMPILE.json 详细请参考链接BSP自查

[github-actions]

👋 感谢您对 RT-Thread 的贡献！Thank you for your contribution to RT-Thread!

为确保代码符合 RT-Thread 的编码规范，请在你的仓库中执行以下步骤运行代码格式化工作流（如果格式化CI运行失败）。
To ensure your code complies with RT-Thread's coding style, please run the code formatting workflow by following the steps below (If the formatting of CI fails to run).

---

🛠 操作步骤 | Steps

1. 前往 Actions 页面 | Go to the Actions page
   点击进入工作流 → | Click to open workflow →

2. 点击 Run workflow | Click Run workflow

• 设置需排除的文件/目录（目录请以"/"结尾）
  Set files/directories to exclude (directories should end with "/")
• 将目标分支设置为 \ Set the target branch to：defunct
• 设置PR number为 \ Set the PR number to：11519

3. 等待工作流完成 | Wait for the workflow to complete
   格式化后的代码将自动推送至你的分支。
   The formatted code will be automatically pushed to your branch.

完成后，提交将自动更新至 defunct 分支，关联的 Pull Request 也会同步更新。
Once completed, commits will be pushed to the defunct branch automatically, and the related Pull Request will be updated.

如有问题欢迎联系我们，再次感谢您的贡献！💐
If you have any questions, feel free to reach out. Thanks again for your contribution!

[github-actions]

📌 Code Review Assignment

🏷️ Tag: kernel

Reviewers: GorrayLi ReviewSun hamburger-os lianux-mm wdfk-prog xu18838022837

Changed Files (Click to expand)

• src/scheduler_comm.c
• src/thread.c
• src/utest/thread_tc.c

---

📊 Current Review Status (Last Updated: 2026-06-26 12:40 CST)

• ⌛ GorrayLi Pending Review
• ⌛ ReviewSun Pending Review
• ⌛ hamburger-os Pending Review
• ⌛ lianux-mm Pending Review
• ⌛ wdfk-prog Pending Review
• ⌛ xu18838022837 Pending Review

---

📝 Review Instructions

1. 维护者可以通过单击此处来刷新审查状态: 🔄 刷新状态
   Maintainers can refresh the review status by clicking here: 🔄 Refresh Status

2. 确认审核通过后评论 LGTM/lgtm
   Comment LGTM/lgtm after confirming approval

3. PR合并前需至少一位维护者确认
   PR must be confirmed by at least one maintainer before merging

ℹ️ 刷新CI状态操作需要具备仓库写入权限。
ℹ️ Refresh CI status operation requires repository Write permission.

[github-actions]

MemBrowse Memory Report

at32f415-start

• ROM: .text +104 B (+0.2%, 65,368 B / 262,144 B, total: 25% used)

esp32-c3

• dram0_0_seg: .dram0.dummy +512 B (+0.2%, 220,352 B / 325,120 B, total: 68% used)
• drom0_0_seg: .eh_frame +40 B, .eh_frame_hdr +8 B (+0.0%, 408,500 B / 8,388,576 B, total: 5% used)
• iram0_0_seg: .iram0.text +96 B, .iram0.text_end +416 B (+0.7%, 74,752 B / 325,120 B, total: 23% used)

gd32105r-start

• CODE: .text +108 B (+0.2%, 52,756 B / 262,144 B, total: 20% used)

hc32f334

• FLASH: .text +104 B (+0.1%, 99,120 B / 131,072 B, total: 76% used)

hpmicro-hpm5301evklite

• ILM: .fast +160 B (+0.4%, 38,224 B / 131,072 B, total: 29% used)
• XPI0: .fast +160 B, .text +8 B (+0.1%, 124,904 B / 1,048,576 B, total: 12% used)

infineon-psoc6

• flash: .text +104 B (+0.1%, 116,248 B / 262,144 B, total: 44% used)

k230

• SRAM: .eh_frame +72 B (+0.0%, 1,122,651 B / 268,300,288 B, total: 0% used)

loongson-ls1cdev

• Code: .text +208 B (+0.1%, 362,712 B)

nordic-nrf51822

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nuvoton-m487

• CODE: .text +112 B (+0.0%, 355,792 B / 524,288 B, total: 68% used)

qemu-virt64-aarch64

• Code: .eh_frame +32 B, .text +128 B (+0.0%, 1,056,460 B)

raspberry-pico-rp2040

• FLASH: .text +152 B (+0.1%, 113,224 B / 2,097,152 B, total: 5% used)

renesas-ra2l1

• FLASH: .text +108 B (+0.1%, 98,164 B / 262,144 B, total: 37% used)

simulator

• Code: .eh_frame +32 B, .eh_frame_hdr +8 B, .rela.dyn +1,080 B, .rodata +192 B, .text +738 B (+0.1%, 2,634,854 B)
• Data: .data +1,280 B (+0.1%, 1,583,776 B)

stm32f407-rt-spark

• CODE: .text +104 B (+0.1%, 85,868 B / 1,048,576 B, total: 8% used)

stm32l475-atk-pandora-llvm

• ROM: .text +100 B (+0.1%, 83,548 B / 524,288 B, total: 16% used)

wch-ch32v208w-r0

• FLASH: .text +152 B (+0.1%, 159,576 B / 491,520 B, total: 32% used)

x86

• Code: .text +160 B (+0.1%, 198,413 B)

xuantie-e901plus

• ISRAM: .text +64 B (+0.1%, 46,360 B / 131,072 B, total: 35% used)
  No memory changes detected for:
• nxp-lpc1114