refactor: rename all chunk flags to include explicit units

Replace ambiguous --chunk-size / --chunk-overlap names that meant different
things in different contexts (tokens vs characters) with fully explicit names:

- --chunk-size (RAG tokens)     → --chunk-tokens
- --chunk-overlap (RAG tokens)  → --chunk-overlap-tokens
- --chunk (enable RAG chunking) → --chunk-for-rag
- --streaming-chunk-size (chars) → --streaming-chunk-chars
- --streaming-overlap (chars)    → --streaming-overlap-chars
- --chunk-size (PDF pages)       → --pdf-pages-per-chunk (poc file)

Also aligns stream_parser.py help with streaming_ingest.py standalone parser.
All 2167 tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_create_arguments.py

@@ -40,8 +40,8 @@ class TestUniversalArguments:
             "verbose",
             "quiet",
             "chunk_for_rag",
-            "chunk_size",
-            "chunk_overlap",  # Phase 2: RAG args from common.py
+            "chunk_tokens",
+            "chunk_overlap_tokens",  # Phase 2: RAG args from common.py
             "preset",
             "config",
             # Phase 2: Workflow arguments (universal workflow support)