Windows: PowerShell 7 execution and runtime portability

[Yuzu02]

Context

Upstream PR #34 already changes command handles from MCP-session scope to workspace scope. This issue tracks the remaining Windows runtime work on top of that branch; it no longer proposes a second shared-process registry or an opt-in --shared-exec-sessions mode.

Problems addressed

1. Windows string commands otherwise inherit subprocess(..., shell=True) behavior and fall through to cmd.exe, which cannot execute native PowerShell syntax.
2. Safe-mode scanning does not recognize PowerShell network cmdlets or recursive deletion aliases/abbreviations.
3. Windows environment variables are case-insensitive, but minimal child environments can contain duplicate casing and omit PATHEXT, preventing executable resolution.
4. Several tests encode POSIX-only shell, newline, home-directory, permission-bit, and cleanup assumptions.
5. Existing Windows typeshed paths expose a small set of Mypy issues.

Implemented design

• PowerShell 7 is required for Windows string commands.
• The server resolves pwsh.exe only from its own trusted environment or the absolute operator setting CODING_TOOLS_MCP_PWSH_PATH.
• No silent cmd.exe fallback.
• PowerShell runs with -NoLogo -NoProfile -NonInteractive.
• Safe mode blocks PowerShell network cmdlets and recursive deletion aliases.
• Windows command environments are normalized case-insensitively and gain a default PATHEXT when needed.
• Cross-platform tests use equivalent native commands and deterministic byte fixtures without changing lossless file semantics.

Validation

Windows 11, PowerShell 7, Python 3.13:

• 217 tests passed
• 0 failures, 0 errors
• 87 explicit POSIX/Linux-only skips
• Ruff clean
• Mypy clean across 16 source files
• uv lock --check clean

Contribution and stack

• Upstream layer 1 PR: Windows: execute string commands with PowerShell 7 #37
• Official GitHub stack Release 0.1.6 OAuth tunnel auth #3 in the contributor fork:
  • Windows: execute string commands with PowerShell 7 Yuzu02/coding-tools-mcp#1
  • Windows: normalize runtime environments and portable tests Yuzu02/coding-tools-mcp#2

GitHub's stacked-PR public preview currently requires every branch to live in the same repository, so it cannot create an upstream stack from a contributor fork. The fork stack preserves the focused diffs; layer 2 can be retargeted upstream after #37 lands or if the branches are adopted upstream.