fix: resolve CI lint errors and Windows test timeout

- Fix gosec G204/G304 warnings by adding exclusions for safe subprocess
  launches and file reads in doctor.go, jira.go, migrate_sync.go, and
  syncbranch/worktree.go
- Fix misspell: "cancelled" -> "canceled" in sync.go
- Fix unparam: mark unused ctx params in jira.go placeholder functions
- Fix errcheck: explicitly ignore fmt.Sscanf return in doctor.go and
  use closure pattern for deferred os.RemoveAll in worktree.go
- Increase Windows test timeout from 10m to 20m to prevent CI timeouts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

cmd/bd/sync.go

@@ -419,7 +419,7 @@ Use --merge to merge the sync branch back to main branch.`,
 									fmt.Printf("✓ Pushed merged changes to %s\n", syncBranchName)
 									pushedViaSyncBranch = true
 								} else {
-									fmt.Println("Push cancelled. Run 'bd sync' again to retry.")
+									fmt.Println("Push canceled. Run 'bd sync' again to retry.")
 									fmt.Println("If this was unintended, use 'git reflog' on the sync branch to recover.")
 								}
 							} else if pullResult.Pushed {