feat: add auto-save functionality for chat conversations

[NB3025]

Issue #, if available: #3322

Description of changes:

This PR adds an automatic conversation saving feature to Q CLI, allowing users to preserve their chat sessions without manually executing the /save command.

Key Features

• Opt-in by default: Auto-save is disabled by default (chat.enableAutoSave = false)
• Session-based file naming: Generates auto-save-YYYYMMDD-HHMMSS.json at session start
• Persistent filename: Uses the same file throughout the session (overwrites on each save)
• Silent operation: No user notifications, errors are logged without interrupting conversations
• Configurable: Two new settings:
  • chat.enableAutoSave (boolean): Enable/disable auto-save
  • chat.autoSavePath (string): Customize file path pattern (default: auto-save-{timestamp}.json)

Implementation Details

Files Changed:

1. crates/chat-cli/src/database/settings.rs (+9 lines)

   • Added ChatEnableAutoSave and ChatAutoSavePath settings

2. crates/chat-cli/src/cli/chat/auto_save.rs (+61 lines, new file)

   • Implemented AutoSaveManager struct
   • Session-based filename generation
   • Silent error handling

3. crates/chat-cli/src/cli/chat/mod.rs (+13 lines)

   • Integrated AutoSaveManager into ChatSession
   • Added auto-save calls after AI response completion (2 locations)

Total code changes: 83 lines

Testing

• ✅ All 327 existing tests pass
• ✅ No impact on existing functionality
• ✅ Manual testing completed:
  • Default disabled state verified
  • Auto-save activation and file generation tested
  • Session persistence confirmed
  • Error handling validated (permission denied, disk full scenarios)
  • Compatibility with existing /save and /load commands verified

Usage Example

bash

Enable auto-save

q settings chat.enableAutoSave true

Start chat (auto-save will create auto-save-20251101-220000.json)

q chat
│ Hello, this will be auto-saved
│ What is 2+2?
│ /quit

File is automatically saved after each AI response

ls auto-save-*.json

Design Decisions

1. Opt-in approach: Respects user choice and avoids unexpected behavior
2. Session-based filename: Prevents file proliferation while maintaining session continuity
3. Silent operation: Minimizes UI clutter and maintains focus on conversation
4. Minimal code footprint: Only 83 lines for complete functionality
5. Independent operation: Works alongside existing save/load features without conflicts

Backward Compatibility

• No breaking changes
• Existing save/load functionality unchanged
• New settings are optional

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