fix(command): resolve fspy program before spawn

[wyf027]

Summary

• Resolve run_command_with_fspy binaries through the same resolve_program path used by run_command.
• Preserve Windows .cmd to PowerShell prefix args before user args when fspy is enabled.
• Update the missing-binary test expectation to match the shared resolver error.

Why

run_command_with_fspy passed the bare binary name directly to fspy::Command::new, so PATH resolution happened inside fspy instead of using Vite+'s resolver. On Windows this can make fspy pick up environment-sensitive shim paths differently from run_command. Reusing resolve_program keeps both command paths aligned and follows the fix direction described in #1599.

Fixes #1599.

Validation

• rustfmt --edition 2024 crates/vite_command/src/lib.rs
• git diff --check
• Confirmed fspy::Command::new<P: AsRef<OsStr>> in voidzero-dev/vite-task at the locked fspy rev accepts the resolved path argument.

Cargo tests could not run in this local checkout because the workspace references rolldown/crates/rolldown_binding/Cargo.toml, but the rolldown/ directory is not present here.

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[wyf027]

Closing this draft PR to avoid duplicating prior unmerged work and adding extra review noise.