chore: include CHANGELOG.md in published npm tarball #1171

Summary

The published @bradygaster/squad-cli npm tarball does not contain a CHANGELOG.md. The GitHub repo has one, but consumers of the npm package — including offline tooling, post-upgrade "what's new" prompts, and editor extensions — cannot show release notes without a network call to GitHub.

Proposal

Include CHANGELOG.md in the published npm tarball.

How:

• Add CHANGELOG.md to the files field in packages/squad-cli/package.json (or the .npmignore allowlist)
• Ensure release tooling stamps it into the published artifact

Why

• Offline-friendly: squad upgrade can show what's-new without internet
• No gh dependency: Tooling does not need GitHub Releases API + auth to show release notes
• Ecosystem convention: Most CLIs ship a CHANGELOG with their package (Keep a Changelog format)
• Enables downstream features: Downstream tamirdresher_microsoft/squad-squad#1 needs a what's-new digest. With a local CHANGELOG, that digest works offline.

Acceptance

• CHANGELOG.md present in published npm tarball (verify with npm pack or npm view ... --json)
• Format follows Keep a Changelog so consumers can programmatically diff between versions
• Release tooling keeps the changelog in sync

Context

Filed during architecture review for downstream tamirdresher_microsoft/squad-squad#1. Companion to:

• channel awareness for self-update.ts
• squad update-check --json CLI command