[GRV-31]: Scaffold human-handoff-linear package contract

[riddim-developer-bot]

Summary

• Add the human-handoff-linear workspace package with bin/, src/, templates/, tests/, package metadata, and README.
• Expose the human-handoff-linear CLI with setup, sync-template, doctor, and bootstrap-project routing.
• Add injected-port use-case modules, value objects, no-op adapters, boundary tests, and the public Human Handoff issue body template.
• Update the Groove use-case catalog for DefineHumanHandoffLinearPackageContract.

Acceptance Criteria Review

• Package shell exists with expected package files and directory structure.
• CLI command and documented subcommands are present in package metadata, README, and help output.
• Core use-case modules use injected ports and are guarded against process.env, node:child_process, and direct fetch usage.
• Checked-in template exists at packages/human-handoff-linear/templates/human-handoff-issue-body.md with public-safe Human Handoff setup wording.
• Command-routing tests cover help output and unknown-command failure without a Linear token.

Verification

• npm test --workspace human-handoff-linear
• npm test
• git diff --check
• LC_ALL=C rg -n "[^\\x00-\\x7F]" packages/human-handoff-linear || true

Skipped checks: none.

CLI Scorecard

Score: 94/100.

Worst findings: no blocking findings. Long-running progress rules are not applicable to this scaffold because commands perform no Linear mutations; future mutation-backed work should add step progress around real network operations.