Stabilize interpreter selection integration tests by asserting on interpreter path, not envId

[Copilot]

interpreterSelection.integration.test.ts was asserting equality on envId.id across setEnvironment → getEnvironment flows. That ID is intentionally non-stable after persistence (manager may re-register with a suffixed opaque ID), which caused CI failures despite selecting the same interpreter.

• Root cause

  • Tests treated envId.id as a stable identity across persistence round-trips.
  • For these flows, stable identity is the interpreter executable path (environmentPath.fsPath).

• Changes in this PR

  • Replaced envId.id equality assertions with environmentPath.fsPath equality in all affected integration tests:
    • setEnvironment persists selection
    • Project selection is independent of global (global + project assertions)
    • Change event includes old and new values
    • File inherits project environment
    • Setting same environment is idempotent
  • Updated assertion message text where needed to reflect path-based interpreter identity.

• Scope

  • Test-only change in src/test/integration/interpreterSelection.integration.test.ts.
  • No production/runtime behavior changes.

assert.strictEqual(
    retrieved.environmentPath.fsPath,
    envToSet.environmentPath.fsPath,
    'Retrieved environment should point to the same interpreter as the one set',
);