conductor(tracks): Add two deferred future tracks

- aggregation_smarter_summaries: Sub-agent summarization, hash-based caching
- system_context_exposure: Expose hidden _SYSTEM_PROMPT for user customization

conductor/tracks/system_context_exposure_20260322/plan.md

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+# Implementation Plan: System Context Exposure
+
+## Phase 1: Backend Changes
+Focus: Make _SYSTEM_PROMPT configurable
+
+- [ ] Task: Audit ai_client.py system prompt flow
+- [ ] Task: Move _SYSTEM_PROMPT to configurable storage
+- [ ] Task: Implement load/save of base system prompt
+- [ ] Task: Modify _get_combined_system_prompt() to use config
+- [ ] Task: Write tests for configurable system prompt
+- [ ] Task: Conductor - User Manual Verification 'Phase 1: Backend Changes'
+
+## Phase 2: UI Implementation
+Focus: Add base prompt editor to AI Settings
+
+- [ ] Task: Add UI controls to _render_system_prompts_panel
+- [ ] Task: Implement checkbox for "Use Default Base"
+- [ ] Task: Implement collapsible base prompt editor
+- [ ] Task: Add "Reset to Default" button
+- [ ] Task: Write tests for UI controls
+- [ ] Task: Conductor - User Manual Verification 'Phase 2: UI Implementation'
+
+## Phase 3: Persistence & Provider Testing
+Focus: Ensure persistence and cross-provider compatibility
+
+- [ ] Task: Verify base prompt persists across app restarts
+- [ ] Task: Test with Gemini provider
+- [ ] Task: Test with Anthropic provider
+- [ ] Task: Test with DeepSeek provider
+- [ ] Task: Test with Gemini CLI adapter
+- [ ] Task: Conductor - User Manual Verification 'Phase 3: Persistence & Provider Testing'
+
+## Phase 4: Safety & Defaults
+Focus: Ensure users can recover from bad edits
+
+- [ ] Task: Implement confirmation dialog before saving custom base
+- [ ] Task: Add validation for empty/invalid prompts
+- [ ] Task: Document the base prompt purpose in UI
+- [ ] Task: Add "Show Diff" between default and custom
+- [ ] Task: Write tests for safety features
+- [ ] Task: Conductor - User Manual Verification 'Phase 4: Safety & Defaults'