fix(ci): use npm pkg set to pin packed versions

`pnpm pkg set` is not implemented (ERR_PNPM_NOT_IMPLEMENTED); pnpm
points to the npm CLI for `pkg` operations. Switch the version pin in
the tgz pack steps to `npm pkg set version=0.0.0`.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: Brooooooklyn

.github/workflows/e2e-test.yml

@@ -112,8 +112,8 @@ jobs:
           # A release commit can leave `packages/{core,cli}` at a published
           # version (e.g. 0.1.22), which would make `pnpm pack` emit
           # `*-0.1.22.tgz` instead. Pin both to 0.0.0 so the names stay stable.
-          (cd packages/core && pnpm pkg set version=0.0.0)
-          (cd packages/cli && pnpm pkg set version=0.0.0)
+          (cd packages/core && npm pkg set version=0.0.0)
+          (cd packages/cli && npm pkg set version=0.0.0)
           cd packages/core && pnpm pack --pack-destination ../../tmp/tgz && cd ../..
           cd packages/cli && pnpm pack --pack-destination ../../tmp/tgz && cd ../..
           # Bun is uniquely strict about peer-dep resolution:

.github/workflows/test-vp-create.yml

@@ -97,8 +97,8 @@ jobs:
           # A release commit can leave `packages/{core,cli}` at a published
           # version (e.g. 0.1.22), which would make `pnpm pack` emit
           # `*-0.1.22.tgz` instead. Pin both to 0.0.0 so the names stay stable.
-          (cd packages/core && pnpm pkg set version=0.0.0)
-          (cd packages/cli && pnpm pkg set version=0.0.0)
+          (cd packages/core && npm pkg set version=0.0.0)
+          (cd packages/cli && npm pkg set version=0.0.0)
           cd packages/core && pnpm pack --pack-destination ../../tmp/tgz && cd ../..
           cd packages/cli && pnpm pack --pack-destination ../../tmp/tgz && cd ../..
           # Bun is uniquely strict about peer-dep resolution: