Summary:
- introduce workflow/api with Session DSL and move ACW/gh/prompt/path helpers
- refactor planner pipeline + CLI to use Session-backed pipeline module
- update impl loop to run Session with input/output overrides
- refresh docs and tests to use workflow/api imports

Files:
- docs/cli/acw.md: point ACW wrapper reference to workflow/api.
- docs/cli/lol.md: note workflow/api usage for lol impl.
- docs/cli/planner.md: update prompt rendering reference to workflow/api.
- docs/feat/draft/api.md: document input/output overrides in Session.run_prompt.
- python/agentize/workflow/__init__.md: reference workflow/api package in module organization.
- python/agentize/workflow/__init__.py: re-export ACW/run_acw from workflow.api.
- python/agentize/workflow/api/README.md: describe workflow API package contents.
- python/agentize/workflow/api/__init__.md: document exported Session/ACW helpers.
- python/agentize/workflow/api/__init__.py: export Session DSL and ACW helpers.
- python/agentize/workflow/api/acw.py: move ACW runner helpers from utils.
- python/agentize/workflow/api/acw.md: document ACW helper interfaces.
- python/agentize/workflow/api/gh.py: move GitHub helper wrappers from utils.
- python/agentize/workflow/api/gh.md: document GitHub helper interfaces.
- python/agentize/workflow/api/path.py: move path helpers from utils.
- python/agentize/workflow/api/path.md: document path helper interfaces.
- python/agentize/workflow/api/prompt.py: move prompt rendering helpers from utils.
- python/agentize/workflow/api/prompt.md: document prompt helper interfaces.
- python/agentize/workflow/api/session.py: implement Session DSL with retries and parallel execution.
- python/agentize/workflow/api/session.md: document Session/StageResult/StageCall/PipelineError.
- python/agentize/workflow/impl/impl.md: describe impl loop using workflow.api and Session overrides.
- python/agentize/workflow/impl/impl.py: refactor impl loop to use Session.
- python/agentize/workflow/planner.md: update deprecated shim to re-export workflow.api.
- python/agentize/workflow/planner.py: update shim imports for workflow.api.
- python/agentize/workflow/planner/README.md: note Session-based pipeline module.
- python/agentize/workflow/planner/__init__.md: reference pipeline module exports.
- python/agentize/workflow/planner/__init__.py: re-export pipeline run_planner_pipeline.
- python/agentize/workflow/planner/__main__.md: document CLI delegating to pipeline.
- python/agentize/workflow/planner/__main__.py: delegate CLI to pipeline and workflow.api helpers.
- python/agentize/workflow/planner/pipeline.md: document Session-based planner pipeline.
- python/agentize/workflow/planner/pipeline.py: implement Session-based planner pipeline.
- python/agentize/workflow/utils/README.md: remove deprecated utils package docs.
- python/agentize/workflow/utils/__init__.md: remove deprecated utils module docs.
- python/agentize/workflow/utils/__init__.py: remove deprecated utils module.
- python/agentize/workflow/utils/acw.md: remove moved ACW docs.
- python/agentize/workflow/utils/acw.py: remove moved ACW implementation.
- python/agentize/workflow/utils/gh.md: remove moved GH docs.
- python/agentize/workflow/utils/gh.py: remove moved GH implementation.
- python/agentize/workflow/utils/path.md: remove moved path docs.
- python/agentize/workflow/utils/path.py: remove moved path implementation.
- python/agentize/workflow/utils/prompt.md: remove moved prompt docs.
- python/agentize/workflow/utils/prompt.py: remove moved prompt implementation.
- python/tests/test_planner_workflow.py: update imports to workflow.api.
- python/tests/test_workflow_session.py: add Session DSL tests.

Issue: #805
Tests: `python -m pytest python/tests/test_workflow_session.py python/tests/test_planner_workflow.py` (passed)