refactor(workflows): move backend module to handler/llm

Co-locate LLM backend implementations (AgentApiBackend, AgentCliBackend,
BackendRouter) under handler/ since they implement the CodergenBackend
trait defined in handler/agent.rs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/crates/fabro-api/src/serve.rs

@@ -15,7 +15,7 @@ use crate::jwt_auth::{AuthMode, AuthStrategy};
 use crate::server::build_router;
 use crate::tls::ClientAuth;
 use fabro_interview::Interviewer;
-use fabro_workflows::backend::AgentApiBackend;
+use fabro_workflows::handler::llm::AgentApiBackend;
 use fabro_workflows::handler::default_registry;
 use fabro_workflows::sandbox_provider::SandboxProvider;
 

lib/crates/fabro-cli/src/commands/resume.rs

@@ -10,7 +10,7 @@ use fabro_config::config::FabroConfig;
 use fabro_interview::{AutoApproveInterviewer, ConsoleInterviewer, Interviewer};
 use fabro_model::{Catalog, Provider};
 use fabro_util::terminal::Styles;
-use fabro_workflows::backend::{AgentApiBackend, AgentCliBackend, BackendRouter};
+use fabro_workflows::handler::llm::{AgentApiBackend, AgentCliBackend, BackendRouter};
 use fabro_workflows::checkpoint::Checkpoint;
 use fabro_workflows::event::{EventEmitter, RunNoticeLevel};
 use fabro_workflows::operations::{

lib/crates/fabro-cli/src/commands/run.rs

@@ -15,7 +15,7 @@ use fabro_config::{project as project_config, run as run_config, sandbox as sand
 use fabro_interview::{AutoApproveInterviewer, ConsoleInterviewer, FileInterviewer, Interviewer};
 use fabro_model::{Catalog, FallbackTarget, Provider};
 use fabro_util::terminal::Styles;
-use fabro_workflows::backend::{AgentApiBackend, AgentCliBackend, BackendRouter};
+use fabro_workflows::handler::llm::{AgentApiBackend, AgentCliBackend, BackendRouter};
 use fabro_workflows::checkpoint::Checkpoint;
 use fabro_workflows::cost::{compute_stage_cost, format_cost};
 use fabro_workflows::devcontainer_bridge;

lib/crates/fabro-workflows/src/handler/llm/api.rs

@@ -16,7 +16,7 @@ use crate::context::{Context, WorkflowContext};
 use crate::cost::compute_stage_cost;
 use crate::error::FabroError;
 use crate::event::WorkflowRunEvent;
-use crate::handler::agent::{CodergenBackend, CodergenResult};
+use super::super::agent::{CodergenBackend, CodergenResult};
 use crate::outcome::StageUsage;
 use fabro_graphviz::graph::Node;
 

lib/crates/fabro-workflows/src/handler/llm/cli.rs

@@ -11,7 +11,7 @@ use crate::context::Context;
 use crate::cost::compute_stage_cost;
 use crate::error::FabroError;
 use crate::event::{EventEmitter, WorkflowRunEvent};
-use crate::handler::agent::{CodergenBackend, CodergenResult};
+use super::super::agent::{CodergenBackend, CodergenResult};
 use crate::outcome::StageUsage;
 use fabro_graphviz::graph::Node;
 

lib/crates/fabro-workflows/src/handler/mod.rs

@@ -1,5 +1,6 @@
 pub mod agent;
 pub mod command;
+pub mod llm;
 pub mod conditional;
 pub mod exit;
 pub mod fan_in;

lib/crates/fabro-workflows/src/lib.rs

@@ -91,7 +91,6 @@ pub fn build_completed_stages(
 pub mod artifact;
 pub mod asset_snapshot;
 pub mod assets;
-pub mod backend;
 pub mod checkpoint;
 pub mod conclusion;
 pub mod condition;

lib/crates/fabro-workflows/tests/daytona_integration.rs

@@ -897,7 +897,7 @@ async fn daytona_parallel_git_branching_e2e() {
 // CLI Backend on Daytona — real CLI tools via exec_command
 // ---------------------------------------------------------------------------
 
-use fabro_workflows::backend::AgentCliBackend;
+use fabro_workflows::handler::llm::AgentCliBackend;
 use fabro_workflows::handler::agent::{CodergenBackend, CodergenResult};
 
 /// Helper: run a real CLI backend test on Daytona.

lib/crates/fabro-workflows/tests/integration.rs

@@ -12,8 +12,8 @@ use fabro_interview::{
 };
 use fabro_llm::provider::Provider;
 use fabro_validate::{validate, validate_or_raise, Severity};
-use fabro_workflows::backend::cli::{parse_cli_response, AgentCliBackend, BackendRouter};
-use fabro_workflows::backend::AgentApiBackend;
+use fabro_workflows::handler::llm::cli::{parse_cli_response, AgentCliBackend, BackendRouter};
+use fabro_workflows::handler::llm::AgentApiBackend;
 use fabro_workflows::checkpoint::Checkpoint;
 use fabro_workflows::context::Context;
 use fabro_workflows::error::FabroError;