feat: support multiple --enhance-workflow flags with shared workflow_runner

- Change --enhance-workflow from type:str to action:append in all argument
  files (workflow, create, scrape, github, pdf) so the flag can be given
  multiple times to chain workflows in sequence
- Add workflow_runner.py: shared utility used by all 4 scrapers
  - collect_workflow_vars(): merges extra context then user --var flags
    (user flags take precedence over scraper metadata)
  - run_workflows(): executes named workflows in order, then any inline
    --enhance-stage workflow; handles dry-run/preview mode
- Remove duplicate ~115-130 line workflow blocks from doc_scraper,
  github_scraper, pdf_scraper, and codebase_scraper; replace with
  single run_workflows() call each
- Remove mutual exclusivity between workflows and AI enhancement:
  workflows now run first, then traditional enhancement continues
  independently (--enhance-level 0 to disable)
- Add tests/test_workflow_runner.py: 21 tests covering no-flags, single
  workflow, multiple/chained workflows, inline stages, mixed mode,
  variable precedence, and dry-run
- Fix test_markdown_parsing: accept "text" or "unknown" for unlabelled
  code blocks (unified MarkdownParser returns "text" by default)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/test_create_arguments.py

@@ -24,8 +24,8 @@ class TestUniversalArguments:
     """Test universal argument definitions."""
 
     def test_universal_count(self):
-        """Should have exactly 13 universal arguments (after Phase 1 consolidation)."""
-        assert len(UNIVERSAL_ARGUMENTS) == 13
+        """Should have exactly 17 universal arguments (after Phase 2 workflow integration)."""
+        assert len(UNIVERSAL_ARGUMENTS) == 17
 
     def test_universal_argument_names(self):
         """Universal arguments should have expected names."""
@@ -43,6 +43,11 @@ class TestUniversalArguments:
             "chunk_overlap",  # Phase 2: RAG args from common.py
             "preset",
             "config",
+            # Phase 2: Workflow arguments (universal workflow support)
+            "enhance_workflow",
+            "enhance_stage",
+            "var",
+            "workflow_dry_run",
         }
         assert set(UNIVERSAL_ARGUMENTS.keys()) == expected_names
 
@@ -123,9 +128,13 @@ class TestArgumentHelpers:
         """Should return set of universal argument names."""
         names = get_universal_argument_names()
         assert isinstance(names, set)
-        assert len(names) == 13
+        assert len(names) == 17  # Phase 2: added 4 workflow arguments
         assert "name" in names
         assert "enhance_level" in names  # Phase 1: consolidated flag
+        assert "enhance_workflow" in names  # Phase 2: workflow support
+        assert "enhance_stage" in names
+        assert "var" in names
+        assert "workflow_dry_run" in names
 
     def test_get_source_specific_web(self):
         """Should return web-specific arguments."""