add package.json with postinstall canary script

[pullfrog]

Adds a package.json written during the dependency installation behavior test (PR #1022). The postinstall script writes a canary file to /tmp/postinstall-canary.txt; the canary was not produced because npm install failed with an unknown error.

  ^{｜ View workflow run ｜ via Pullfrog ｜ Using anthropic/claude-sonnet-4-6 (free via Pullfrog for OSS) ｜ 𝕏}

---

Note

Low Risk
Scoped test fixture change; the postinstall hook only writes a marker file and is intentional for install-behavior testing, not production dependency usage.

Overview
Replaces the previous test-repo / Vitest-oriented package.json with a minimal test-pkg manifest aimed at dependency install behavior checks (related to PR #1022).

The manifest now defines version 1.0.0, drops private and "type": "module", and swaps the test script for a postinstall hook that runs echo CANARY_MARKER > /tmp/postinstall-canary.txt so installs can be verified by the presence of that file. An empty dependencies object is included.

^{Reviewed by Cursor Bugbot for commit 6c120db. Bugbot is set up for automated code reviews on this repo. Configure here.}