test: batch 1 — add 80 Bad/Ugly tests for paths, plan, status, shutdown, forge cmds
Fill missing Good/Bad/Ugly categories for:
- paths.go: LocalFs, WorkspaceRoot, CoreRoot, PlansRoot, AgentName, GitHubOrg, parseInt, DefaultBranch
- plan.go: planCreate/Read/Update/Delete/List Ugly, planPath Ugly, validPlanStatus Ugly
- status.go: writeStatus Bad, status Good/Bad
- shutdown.go: dispatchStart/shutdownGraceful Bad/Ugly, shutdownNow Ugly
- commands_forge.go: all 9 cmd* functions Ugly (with httptest mocks)
- sanitise.go: Bad/Ugly for all 5 functions
- prep.go: various lifecycle Bad/Ugly
Gap: 260 → 208 missing categories
Tests: 566 → 646 (+80)
Coverage: 74.4%
Co-Authored-By: Virgil <virgil@lethean.io>