Refactor subagent and workflow domain models; migrate access tiers and events to domain module

- Moved `AccessTier` and `SubagentEvent` enums to `zesdex_domain::subagent`.
- Consolidated workflow-related types into `zesdex_domain::workflow`.
- Updated references across the codebase to use the new domain models.
- Refactored tool execution logic to utilize a new `ToolExecutor` trait.
- Enhanced `AgentTurnService` to handle tool calls and events more effectively.
- Adjusted API handlers and state management to align with new domain structure.

apps/infrastructure/src/subagent/division.rs

@@ -6,19 +6,7 @@
 
 use crate::tools::Tool;
 
-/// Access tier for subagent tool permissions.
-///
-/// Tiers are cumulative: `Write` includes everything in `Read`, and `Full`
-/// includes everything in `Write`.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum AccessTier {
-    /// Read-only: search, read, glob, utility tools (no mutations).
-    Read,
-    /// Read + Write: above plus write, edit, delete, git, memory.
-    Write,
-    /// Full: above plus bash, shell, LSP, workflow, plan tools.
-    Full,
-}
+pub use zesdex_domain::subagent::AccessTier;
 
 /// Filter the available tools to match the given access tier.
 ///