Repo move: point npm, NuGet and release metadata at github/squad #2406

The repo moved from bradygaster/squad to github/squad. Package and release metadata still names the old owner.

Broken

• squad-npm-publish.yml publishes with --provenance. npm rejects a provenance publish when package.json repository.url doesn't match the source repository, and all three published manifests still point at bradygaster/squad.
• NuGet Trusted Publishing for squad-agents-ai-release.yml is still bound to owner bradygaster on nuget.org.

Stale (works only through redirects)

• Squad.Agents.AI project and repository URLs.
• scripts/install.sh and scripts/generate-packaging.mjs defaults.
• The WinGet DocumentUrl. The old docs host now returns 404.
• Hardcoded release links in the standalone release workflow.

Needs a maintainer

• On nuget.org, add a Trusted Publishing policy: Owner github, Repository squad, Workflow squad-agents-ai-release.yml, no environment. Then retire the bradygaster policy.

These stay on purpose: the npm scope @bradygaster/*, the WinGet IDs bradygaster.Squad*, and the Homebrew tap bradygaster/homebrew-squad, which didn't move.