feat: enhance observability across workflows

- Added observability spans to the `governed-rag-index.workflow.ts` for the `indexDocumentsStep`, capturing input data and execution time.
- Integrated observability spans in `learning-extraction-workflow.ts`, including metrics for extraction and human approval steps, improving error handling and performance tracking.
- Implemented spans in `marketingCampaignWorkflow.ts` for both planning and content creation steps, allowing for better monitoring of campaign processes.
- Enhanced `repo-ingestion-workflow.ts` with spans for scanning and ingesting files, providing detailed insights into file processing.
- Updated `research-synthesis-workflow.ts` to include spans for initializing research, researching topics, synthesizing research, and generating reports, improving error reporting and performance metrics.
- Added observability spans in `safe-refactoring-workflow.ts` for generating and verifying refactors, enhancing error tracking and response time metrics.
- Integrated spans in `spec-generation-workflow.ts` for planning, generating PRDs, architectures, and tasks, allowing for better monitoring of the specification generation process.
- Enhanced `stock-analysis-workflow.ts` with spans for fetching stock data, getting company news, running analysis, and generating reports, improving observability and error handling.