feat: add memory system activity display

Implements issue #118 to display auto-memory system operations and
provide a browser for viewing memory files.

Backend changes:
- Detect memory file operations in format_tool_description()
- Add emoji icons (📝/💾) for memory Read/Write/Edit operations
- Add list_memory_files() Tauri command to find all memory files
- Add 4 new tests for memory detection logic
- Update Tauri capabilities to allow reading .claude directory

Frontend changes:
- Create MemoryBrowserPanel component with file list and viewer
- Add memory panel to main app layout
- Support Markdown rendering of memory file contents
- Add loading states and error handling

Testing:
- All 354 Rust tests passing
- TypeScript type-checks pass

Co-Authored-By: Hikari <hikari@nhcarrigan.com>

src-tauri/Cargo.lock

@@ -1636,7 +1636,7 @@ checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
 [[package]]
 name = "hikari-desktop"
-version = "1.3.0"
+version = "1.4.0"
 dependencies = [
  "chrono",
  "dirs 5.0.1",