fix(security): restrict Windows private files with fail-safe ACL ordering

[raymondginger2018-sudo]

Summary

Redoes the Windows private-file ACL restriction from #148 in a fail-safe order, addressing the exact regression that forced the revert in #158.

Why #148 was reverted (#158)

The original _restrict_windows_acl() ran:

1. icacls <path> /inheritance:r (strip inherited ACEs)
2. icacls <path> /grant:r <user>:F (grant the current user)

If the grant failed (service account, transient timeout, ...), the path had already lost every inherited ACE and had no usable ACE for the current user — the file became unopenable, surfacing as sqlite3.OperationalError: attempt to write a readonly database on the Windows lifecycle CI job.

This fix — grant first, strip second, fail safe

_restrict_windows_acl() now:

1. Grants the current user full control first: icacls <path> /grant:r <user>:F
2. Only if the grant succeeds, strips inherited ACEs: icacls <path> /inheritance:r
3. Grant fails → return, leaving the inherited ACLs untouched; the path stays accessible.
4. Strip fails → the path is merely less restricted, still fully usable.

The identity is resolved via whoami (mbcs encoding, errors="replace"), same as the original PR.

Wiring

_restrict_windows_acl() is applied at every private-storage entry point on Windows:

• open_private_file() — Windows branch calls _restrict_windows_acl(target) instead of no-op
• harden_private_tree() — removed the if os.name == "nt": return base early exit so the tree walk repairs ACLs too
• _chmod() — Windows branch calls _restrict_windows_acl(path) instead of returning early

Tests

New tests/test_private_storage_windows.py (Windows-only, skipped elsewhere) asserts:

• Dangerous well-known ACEs (Everyone, Authenticated Users, BUILTIN\Users) are removed after restriction
• The current user retains Full Control (F) after restriction
• Covers private directories, private files, and full tree hardening

Verified locally on Windows (3 passed) and POSIX suite unaffected (8 skipped as expected).

References

• Original PR: fix(security): restrict Windows private files to the current user #148 (reverted by Revert Windows private-file ACL restriction (broke main) #158)
• Revert PR: Revert Windows private-file ACL restriction (broke main) #158 — feedback: "The idea is right, ordering just needs to fail safe."

[raymondginger2018-sudo]

@Zongwei9888 您好，已处理 CI 失败，请帮忙 review：

1. Linting 失败已修复 — tests/test_private_storage_windows.py 中 _acl_lines 的列表推导式已按 ruff format 折叠为单行（commit 147a539）。

2. Bundle macOS x64 失败是 GitHub Actions 基础设施故障 — 失败发生在 "Set up job" 阶段（Failed to resolve action download info. Error: Service Unavailable → Internal Server Error），早于 checkout，与代码无关；Linux x64 / Windows x64 / macOS arm64 均通过。重跑即可。

3. 背景说明 — #148 合并后因 ACL 操作非原子（先 /inheritance:r 再 /grant:r，grant 失败时路径已剥离继承 ACE → 只读数据库）被 #158 revert。本 PR 以 fail-safe 顺序重做：先 grant 当前用户完全控制，成功后才剥离继承 ACE；grant 失败则 ACL 原样保留，strip 失败仅导致限制更宽松，不会出现只读问题。

请批准 CI 运行并 review，谢谢！

[raymondginger2018-sudo]

@Zongwei9888 您好，已处理 CI 失败，请帮忙 review：

1. Linting 失败已修复 — tests/test_private_storage_windows.py 中 _acl_lines 的列表推导式已按 ruff format 折叠为单行（commit 147a539）。

2. Bundle macOS x64 失败是 GitHub Actions 基础设施故障 — 失败发生在 "Set up job" 阶段（Failed to resolve action download info. Error: Service Unavailable → Internal Server Error），早于 checkout，与代码无关；Linux x64 / Windows x64 / macOS arm64 均通过。重跑即可。

3. 背景说明 — #148 合并后因 ACL 操作非原子（先 /inheritance:r 再 /grant:r，grant 失败时路径已剥离继承 ACE → 只读数据库）被 #158 revert。本 PR 以 fail-safe 顺序重做：先 grant 当前用户完全控制，成功后才剥离继承 ACE；grant 失败则 ACL 原样保留，strip 失败仅导致限制更宽松，不会出现只读问题。

请批准 CI 运行并 review，谢谢！

[raymondginger2018-sudo]

@Zongwei9888 您好，补充一个关于 Security CI "Dependency and license audit" 失败的分析：

该 check 失败在 "Audit Node dependencies" 步骤（npm ci && npm audit --audit-level=high）。经查 Security CI 运行历史：

• main 分支最近一次 Security CI（run [Feature Request]: .gitignore update #43，08-07 08:45）为 success；
• 本 PR 的 run [Bug]: Error when starting deepcode #44（08-08 11:22）失败。

本 PR 仅修改 core/private_storage.py 与 tests/test_private_storage_windows.py，未触碰 desktop/ 依赖树。代码无差异、仅有时间差异，推断失败原因是 8/7–8/8 之间 npm registry 发布了新的高危漏洞公告，使 npm audit --audit-level=high 从绿变红——这与 PR 代码无关，是上游依赖需要升级（类似 #166 raise aiohttp floor 的处理方式）。

如确认该判断，可忽略此 check 或触发依赖升级。谢谢！