feat: optimize make targets for issue management - Issue #137

Standardize all issue management make targets to use consistent "issue-" prefix:
- list-issues → issue-list
- show-issue → issue-show
- list-open-issues → issue-list-open
- create-issue → issue-create
- close-issue → issue-close
- close-issue-enhanced → issue-close-enhanced
- close-issues-batch → issue-close-batch
- issues-get → issue-get
- issues-csv → issue-csv
- issues-json → issue-json
- issues-high → issue-high

Updated .PHONY declarations, help text, and error messages.
Updated TestCLIConsolidation::test_make_targets_work to validate new conventions.
All issue management targets now follow consistent naming pattern.

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

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

tests/test_cli_consolidation.py

@@ -170,10 +170,10 @@ class TestCLIConsolidation:
         if makefile_path.exists():
             makefile_content = makefile_path.read_text()
 
-            # Check for issue-related targets
+            # Check for issue-related targets (using new issue- prefix convention)
             expected_targets = [
-                "close-issue", "close-issue-enhanced", "close-issues-batch",
-                "list-issues", "show-issue"
+                "issue-close", "issue-close-enhanced", "issue-close-batch",
+                "issue-list", "issue-show"
             ]
 
             for target in expected_targets: