fix: make the generated CLI client's session walk work on Windows

[mikeasick-fennec]

What was broken

The generated CLI client resolves the calling session's bridge by walking the process
tree. That walk worked on Linux, macOS, and other Unix -- it read each parent PID from
/proc, then ps. Neither exists on Windows, so the walk saw only the immediate parent
(cmd.exe, never in BRIDGES) and fell back to any live bridge. Two sessions sharing a
CLI name could misroute on Windows.

What this changes

• windows_parent_pid(): reads the parent PID from a CreateToolhelp32Snapshot via
  ctypes -- standard library, no new dependency.
• ancestors() now goes through a shared parent_pid() dispatcher that selects by
  os.name between two per-OS leaves -- unix_parent_pid (the existing /proc then
  ps lookup) and the new windows_parent_pid. Dispatching by os.name also keeps a
  stray ps on PATH (e.g. Git for Windows) from short-circuiting the native lookup.
  The walk itself stays platform-neutral.
• A cross-platform e2e test: a live decoy bridge keyed first under a non-ancestor PID,
  the real bridge under the test process's PID; the client must pick the real one or it
  falls back to the decoy and fails. Runs the .cmd on Windows and the sh script on
  Unix.

Checked

• New e2e test passes locally on Windows, exercising the real .cmd -> python ->
  ctypes walk; CI exercises the sh -> /proc/ps path.
• rustfmt and clippy clean on the change.

Follows #231 (the shared-program Windows .cmd client) -- the process-tree walk was the
remaining place multi-session bridge selection was still Unix-only.

🤖 Generated with Claude Code

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[Copilot]

Pull request overview

This PR fixes multi-session bridge disambiguation for the generated CLI client on Windows by making the process-tree walk work without relying on Unix-only facilities (/proc, ps). It introduces a Windows-specific parent-PID lookup and adds an e2e test to ensure the client selects the correct session bridge even when a live decoy exists.

Changes:

• Add a Windows ctypes implementation to retrieve a process’s parent PID via Toolhelp snapshots.
• Refactor the Python client’s ancestor walk to use a shared parent_pid() dispatcher (Windows vs Unix leaf implementations).
• Add an end-to-end test that fails if the client falls back to a live decoy bridge instead of selecting the ancestor-session bridge.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
crates/mcp-compressor-core/src/client_gen/cli.rs	Adds Windows parent-PID lookup and refactors ancestor walk to be platform-neutral with OS-specific leaf functions.
crates/mcp-compressor-core/tests/generated_clients.rs	Adds an e2e regression test to verify correct bridge selection in multi-session scenarios (including Windows .cmd execution path).

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