Fix the verified bugs from the review

[SimonCropp]

The verified bugs from the review in todo.md, one fix each.

• Attached viewer's context menu closed within 200ms. Sync replaced the queue and cleared the menu on every poll, even when nothing changed. An unchanged listing now returns the state as it was, and a changed one keeps the menu while the entries are the same ones in the same places.
• One quoted PATH entry broke DiffTools on .NET Framework. Path.Combine throws on the quote, from the static constructor that reads PATH. Entries are now unquoted, and empty or invalid ones dropped.
• DiffEngineViewer left right never exited while the tray ran. Closing hid the window in file mode too, where nothing can show it again. Hiding is now for inline mode only.
• F# double-backtick test names got no member narrowing. The backtick before the name is not a declaring keyword, so the member was never found. Declarations are now judged from before the opening backticks.
• An empty entry-point name hung the patcher under the file's mutex. Empty names are skipped.
• Copying a whole side turned tabs into spaces. It now copies the file's lines rather than the flattened screen text.
• Linux shortcuts followed key position rather than layout, so on AZERTY the key labelled Q accepted. Letters are now read as typed characters.
• The inline applier's mutex was per terminal session on Linux and macOS, so an IDE and a viewer started from a terminal did not exclude each other. It is machine wide there now, falling back to the session name.
• ProcessCleanup killed by a PID from a list taken once per run, which a closed tool's reused PID made into an unrelated process. A hit is now re-checked against that process's command line, and tools launched in the run are added to the list.
• The render loop took the session lock every frame, behind an accept that can wait ten seconds on the applier's mutex. Frames with no input no longer take it.
• A wire accept checked for a conflict outside the lock. The lookup and the refusal now happen in the mutation that acts.

The Linux key change is in native/src/deview.cpp, so this push runs build-native, which should open its own PR with the rebuilt binaries.

Run locally on Windows, all passing: DiffEngine.Tests 703, DiffEngineViewer.Tests 359, DiffEngineTray.Tests 246, and a Release build of the solution.