v4.1.0 - Reactive Linear issue spillover

Highlights

• Adds reactive Linear issue spillover for direct GraphQL graph apply when Linear rejects an issue description for size or character limits.
• Adds --spillover-dir and project.spilloverDir so spillover docs can be routed to a known local context root.
• Keeps normal issues lightweight: Linear is tried first, and local per-issue docs are only created after an actual Linear rejection.
• Adds fake Linear limit coverage, read-back tolerance for spillover pointer bodies, and dogfood fake-state setup.

Verification

• CI test: passed
• CodeQL analyze: passed
• Local shell syntax, Python tests, evaluators, temp install check, README completeness, and publisher secret preflight passed.