Add Clifford simulation across VS Code runs, tests, and debugging

[Michael Goulding (MichaelGoulding)]

Summary

• add a VS Code setting to select sparse state-vector or Clifford stabilizer simulation
• use the selected simulator for Run program, Run file and show histogram, Test Explorer, and debugging
• preserve sparse simulation as the default and keep existing callers source-compatible
• support the existing Pauli-noise and qubit-loss settings with Clifford simulation
• warn and continue when Q# calls DumpMachine under Clifford simulation

User experience

Select Q# › Simulation: Type in VS Code Settings, or add:

{
  "Q#.simulation.type": "clifford",
  "Q#.simulation.clifford.maxQubits": 1000
}

Q#.simulation.type offers:

• sparse — default; supports arbitrary quantum programs
• clifford — efficient stabilizer simulation for Clifford-only programs

Q#.simulation.clifford.maxQubits accepts integers from 1 through 10,000 and defaults to 1,000. The public qsharp-lang run and debug APIs apply the same validation.

Behavior and limitations

• unsupported non-Clifford gates and rotations report simulator diagnostics
• Q#.simulation.pauliNoise and Q#.simulation.qubitLoss are supported for Clifford histogram execution
• scalar qubit loss uses the same per-operation ordering and lost-qubit behavior as the sparse simulator; cumulative noise configurations continue to use the stabilizer simulator's native loss policies
• dynamic in-program ConfigureQubitLoss remains unsupported in Clifford simulation
• Q# DumpMachine emits a warning and execution continues because Clifford simulation cannot provide amplitudes without potentially exponential work
• the debugger supports stepping, locals, breakpoints, and circuit tracing, but omits the amplitude-based Quantum State scope under Clifford simulation
• programmatic debugger state capture continues to report that Clifford state visualization is unsupported

Testing

• Rust evaluator/compiler suites: 618 qsc_eval tests passed; 464 qsc tests passed with 1 ignored
• focused Clifford loss tests cover backend behavior, interpreter execution, legacy lost-qubit gate semantics, and direct/WebWorker npm execution
• package-level Clippy passed for qsc_eval and qsc; WASM and Python packages passed cargo check
• VS Code language-service suite: 19/19 browser and 19/19 desktop
• WASM, npm, and VS Code extension build
• Prettier, Rust formatting, and diff checks

The Python package compiles locally, but its native test binary cannot launch in this environment because the GPU runtime DLL is unavailable; CI will exercise the package tests.