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/doctor.go

@@ -2515,7 +2515,7 @@ func checkSyncBranchHealth(path string) doctorCheck {
 		fileCount := len(strings.Split(diffFiles, "\n"))
 		// Parse ahead count as int for comparison
 		aheadCountInt := 0
-		fmt.Sscanf(aheadCount, "%d", &aheadCountInt)
+		_, _ = fmt.Sscanf(aheadCount, "%d", &aheadCountInt)
 
 		// Only warn if significantly behind (20+ commits AND 50+ source files)
 		// Small drift is normal between bd sync operations

cmd/bd/jira.go

@@ -642,7 +642,7 @@ func detectJiraConflicts(ctx context.Context) ([]JiraConflict, error) {
 // reimportConflicts re-imports conflicting issues from Jira (Jira wins).
 // NOTE: This is a placeholder - full implementation requires fetching individual
 // issues from Jira API and updating local copies.
-func reimportConflicts(ctx context.Context, conflicts []JiraConflict) error {
+func reimportConflicts(_ context.Context, conflicts []JiraConflict) error {
 	if len(conflicts) == 0 {
 		return nil
 	}
@@ -657,7 +657,7 @@ func reimportConflicts(ctx context.Context, conflicts []JiraConflict) error {
 // resolveConflictsByTimestamp resolves conflicts by keeping the newer version.
 // NOTE: This is a placeholder - full implementation requires fetching Jira
 // timestamps and comparing with local timestamps.
-func resolveConflictsByTimestamp(ctx context.Context, conflicts []JiraConflict) error {
+func resolveConflictsByTimestamp(_ context.Context, conflicts []JiraConflict) error {
 	if len(conflicts) == 0 {
 		return nil
 	}

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 {