fix: Resolve all CI failures (ruff linting + MCP test failures)

Fixed 7 ruff linting errors:
- SIM102: Simplified nested if statements in rag_chunker.py
- SIM113: Use enumerate() in streaming_ingest.py
- ARG001: Prefix unused signal handler args with underscore
- SIM105: Replace try-except-pass with contextlib.suppress (3 instances)

Fixed 7 MCP server test failures:
- Updated generate_config_tool to output unified format (not legacy)
- Updated test_validate_valid_config to use unified format
- Renamed test_submit_config_accepts_legacy_format to
  test_submit_config_rejects_legacy_format (tests rejection, not acceptance)
- Updated all submit_config tests to use unified format:
  - test_submit_config_requires_token
  - test_submit_config_from_file_path
  - test_submit_config_detects_category
  - test_submit_config_validates_name_format
  - test_submit_config_validates_url_format

Added v3.0.0 release planning documents:
- RELEASE_EXECUTIVE_SUMMARY_v3.0.0.md (one-page overview)
- RELEASE_PLAN_v3.0.0.md (complete 4-week campaign)
- RELEASE_CONTENT_CHECKLIST_v3.0.0.md (content creation guide)

All tests should now pass. Ready for v3.0.0 release.

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

src/skill_seekers/cli/rag_chunker.py

@@ -352,9 +352,8 @@ class RAGChunker:
 
             # Add chunk if it meets minimum size requirement
             # (unless the entire text is smaller than target size)
-            if chunk_text.strip():
-                if len(text) <= target_size_chars or len(chunk_text) >= min_size_chars:
-                    chunks.append(chunk_text)
+            if chunk_text.strip() and (len(text) <= target_size_chars or len(chunk_text) >= min_size_chars):
+                chunks.append(chunk_text)
 
             # Move to next chunk with overlap
             if j < len(boundaries) - 1: