fix(create): pin new libraries to the creating CLI version

[SaKaNa-Y]

Problem

Running vp create vite:library --package-manager npm with Vite+ 0.3.2 generates a project with mismatched toolchain versions:

• vite-plus is declared as ^0.2.4 and installs as 0.2.9.
• The vite override points to @voidzero-dev/vite-plus-core@0.3.2.

The library comes from a remote template whose Vite+ dependency can lag behind the CLI. Scaffolding preserves that dependency, while project setup writes the current CLI's core override. The reproduced project still passes its checks, test and packaging; the confirmed defect is the version mismatch.

Fix

Set the newly downloaded built-in library's vite-plus dev dependency to VITE_PLUS_VERSION before project integration. The dependency and toolchain override then use the same version, and subsequent workspace integration can still convert the dependency to a catalog reference.

The change is confined to vite:library creation. It preserves unrelated dependencies and the existing migration rules for user-owned version pins, including the boundary established in #1697.

Verification

• Regression tests fail before the fix and pass afterward for standalone and workspace library scaffolding.
• Full unit suite: 1,210 passed, 1 skipped. Formatting, lint and type checks passed.
• cargo test -p vp_cli_snapshots --offline -- create_library_npm: 1 case passed, asserting that both the declared and installed Vite+ versions match the core override.
• Manual npm workflow: the generated dependency and installed package are both 0.3.2; project checks, its test and library packaging pass.

The full CLI snapshot suite was not run; CLI verification covered the npm library case above.