3c850b8ffc
New build_workspace_guidance(available_tools) returns a single guidance block that grows with which workspace tools are present. Core paragraph appears when workspace_search is available; retrieve/list/index add their own paragraphs when those tools are also available. workspace_delete is intentionally not prompted (destructive). Follows the existing MEMORY_GUIDANCE/SESSION_SEARCH_GUIDANCE/SKILLS_GUIDANCE pattern in agent/prompt_builder.py.