fix: resolve 18 bugs and code quality issues across adaptors, CLI, and chunking pipeline

Bug fixes:
- Fix --var flag silently dropped in create routing (args.workflow_var → args.var)
- Fix double _score_code_quality() call in word scraper
- Add .docx file extension validation in WordToSkillConverter
- Fix weaviate ImportError masked by generic Exception handler
- Fix RAG chunking crash using non-existent converter.output_dir

Chunking pipeline improvements:
- Wire --chunk-overlap-tokens through entire package pipeline
  (package_skill → adaptor.package → format_skill_md → _maybe_chunk_content → RAGChunker)
- Add auto-scaling overlap: max(50, chunk_tokens//10) when chunk size is non-default
- Rename --no-preserve-code to --no-preserve-code-blocks (backward-compat alias kept)
- Replace hardcoded 512/50 chunk defaults with DEFAULT_CHUNK_TOKENS/DEFAULT_CHUNK_OVERLAP_TOKENS
  constants across all 12 concrete adaptors, rag_chunker, base, and package_skill

Code quality:
- Extract shared _generate_openai_embeddings() and _generate_st_embeddings() to SkillAdaptor
  base class, removing ~150 lines of duplication from chroma/weaviate/pinecone
- Add Pinecone adaptor with full upload support (pinecone_adaptor.py)

Tests (14 new):
- chunk_overlap_tokens parameter wiring, auto-scaling overlap, preserve_code_blocks flag
- .docx/.doc/no-extension file validation, --var flag routing E2E
- Embedding method inheritance verification, backward-compatible flag aliases

Docs:
- Update CHANGELOG, CLI_REFERENCE, API_REFERENCE, packaging guide (EN+ZH)
- Update README test count badge (1880+ → 2283+)

All 2283 tests passing, 8 skipped, 0 failures.

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

src/skill_seekers/cli/arguments/package.py

@@ -8,6 +8,8 @@ import and use these definitions.
 import argparse
 from typing import Any
 
+from .common import DEFAULT_CHUNK_TOKENS, DEFAULT_CHUNK_OVERLAP_TOKENS
+
 PACKAGE_ARGUMENTS: dict[str, dict[str, Any]] = {
     # Positional argument
     "skill_directory": {
@@ -49,6 +51,7 @@ PACKAGE_ARGUMENTS: dict[str, dict[str, Any]] = {
                 "chroma",
                 "faiss",
                 "qdrant",
+                "pinecone",
             ],
             "default": "claude",
             "help": "Target LLM platform (default: claude)",
@@ -109,13 +112,22 @@ PACKAGE_ARGUMENTS: dict[str, dict[str, Any]] = {
         "flags": ("--chunk-tokens",),
         "kwargs": {
             "type": int,
-            "default": 512,
-            "help": "Maximum tokens per chunk (default: 512)",
+            "default": DEFAULT_CHUNK_TOKENS,
+            "help": f"Maximum tokens per chunk (default: {DEFAULT_CHUNK_TOKENS})",
             "metavar": "N",
         },
     },
-    "no_preserve_code": {
-        "flags": ("--no-preserve-code",),
+    "chunk_overlap_tokens": {
+        "flags": ("--chunk-overlap-tokens",),
+        "kwargs": {
+            "type": int,
+            "default": DEFAULT_CHUNK_OVERLAP_TOKENS,
+            "help": f"Overlap between chunks in tokens (default: {DEFAULT_CHUNK_OVERLAP_TOKENS})",
+            "metavar": "N",
+        },
+    },
+    "no_preserve_code_blocks": {
+        "flags": ("--no-preserve-code-blocks",),
         "kwargs": {
             "action": "store_true",
             "help": "Allow code block splitting (default: code blocks preserved)",
@@ -130,3 +142,11 @@ def add_package_arguments(parser: argparse.ArgumentParser) -> None:
         flags = arg_def["flags"]
         kwargs = arg_def["kwargs"]
         parser.add_argument(*flags, **kwargs)
+
+    # Deprecated alias for backward compatibility (removed in v4.0.0)
+    parser.add_argument(
+        "--no-preserve-code",
+        dest="no_preserve_code_blocks",
+        action="store_true",
+        help=argparse.SUPPRESS,
+    )