Refactor workflow signatures to typed Pydantic outputs

[Dan-StrategicAutomation]

Motivation

• Consolidate multiple raw DSPy output fields into single, typed Pydantic result models to improve schema clarity and DSPy introspection for workflow agents and tools.
• Make compression inputs/outputs structured so KB compression and callers use explicit models instead of loosely-typed primitives.

Description

• Added shared workflow schemas in agents/schema/base.py: WorkflowResult, MarkdownCompressionRequest, and MarkdownCompressionResult.
• Added typed workflow result models in agents/schema/workflow.py: PlanExecutionResult, TodoResolutionResult, TriagePresentation, and GeneratedAgentSpec, and exported them via agents/schema/__init__.py.
• Replaced multi-field outputs on signatures with single nested model outputs in agents/workflow/work_plan_executor.py, agents/workflow/work_todo_executor.py, agents/workflow/triage_agent.py, and agents/workflow/agent_generator.py (now use execution_result, resolution_result, triage_presentation, and generated_agent).
• Wrapped KB compression signature in utils/knowledge/compression.py to accept MarkdownCompressionRequest and return MarkdownCompressionResult, and updated call sites and callers in workflows to read nested model attributes.
• Added tests/test_workflow_signature_models.py asserting the modified signatures use the new structured Pydantic models and that the models behave as expected.

Testing

• Ran python -m compileall on the touched modules which succeeded and confirmed there are no syntax errors in the modified files.
• Ran ruff check for the modified files (agents/schema/base.py, agents/schema/workflow.py, agents/schema/__init__.py, agents/workflow/*, utils/knowledge/compression.py, workflows/*, and the new test) and fixed line-length/formatting issues; those checks for the changed files passed.
• Added unit tests in tests/test_workflow_signature_models.py and compiled them, but full pytest could not be executed in this environment due to missing project dependencies (e.g., pydantic) and network failures when attempting dependency installation.
• Note: a repository-wide lint run flagged pre-existing issues outside the touched files; the changes in this PR are self-consistent and lint-clean after targeted fixes.

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Codex Task