refactor: remove sandbox system and simplify agent architecture

Remove the entire sandbox security system including:
- All sandbox-related Rust code and dependencies (gaol crate)
- Sandbox command handlers and platform-specific implementations
- Comprehensive test suite for sandbox functionality
- Agent sandbox settings UI components

Simplify agent configuration by removing sandbox and permission fields:
- Remove sandbox_enabled, enable_file_read, enable_file_write, enable_network from agent configs
- Update all CC agents to use simplified configuration format
- Remove sandbox references from documentation and UI

src-tauri/Cargo.lock

@@ -680,7 +680,6 @@ dependencies = [
  "dirs 5.0.1",
  "env_logger",
  "futures",
- "gaol",
  "glob",
  "headless_chrome",
  "libc",
@@ -1640,16 +1639,6 @@ dependencies = [
  "byteorder",
 ]
 
-[[package]]
-name = "gaol"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "061957ca7a966a39a79ebca393a9a6c7babda10bf9dd6f11d00041558d929c22"
-dependencies = [
- "libc",
- "log",
-]
-
 [[package]]
 name = "gdk"
 version = "0.18.2"