refactor: break up dispatch_task() into helper functions (#1137)

Extract three helpers from the 108-line dispatch_task() function:
- _validate_task() — precondition checks (title required)
- _select_dispatch_strategy() — decides gitea vs api vs local
- _log_dispatch_result() — logging for failed attempts

Main dispatch_task() now orchestrates: validate → resolve → select strategy → dispatch → log/escalate.

Fixes #1137

src/timmy/dispatcher.py

@@ -686,6 +686,80 @@ async def _dispatch_local(
 # ---------------------------------------------------------------------------
 
 
+def _validate_task(
+    title: str,
+    task_type: TaskType | None,
+    agent: AgentType | None,
+    issue_number: int | None,
+) -> DispatchResult | None:
+    """Validate task preconditions.
+
+    Args:
+        title: Task title to validate.
+        task_type: Optional task type for result construction.
+        agent: Optional agent for result construction.
+        issue_number: Optional issue number for result construction.
+
+    Returns:
+        A failed DispatchResult if validation fails, None otherwise.
+    """
+    if not title.strip():
+        return DispatchResult(
+            task_type=task_type or TaskType.ROUTINE_CODING,
+            agent=agent or AgentType.TIMMY,
+            issue_number=issue_number,
+            status=DispatchStatus.FAILED,
+            error="`title` is required.",
+        )
+    return None
+
+
+def _select_dispatch_strategy(agent: AgentType, issue_number: int | None) -> str:
+    """Select the dispatch strategy based on agent interface and context.
+
+    Args:
+        agent: The target agent.
+        issue_number: Optional Gitea issue number.
+
+    Returns:
+        Strategy name: "gitea", "api", or "local".
+    """
+    spec = AGENT_REGISTRY[agent]
+    if spec.interface == "gitea" and issue_number is not None:
+        return "gitea"
+    if spec.interface == "api":
+        return "api"
+    return "local"
+
+
+def _log_dispatch_result(
+    title: str,
+    result: DispatchResult,
+    attempt: int,
+    max_retries: int,
+) -> None:
+    """Log the outcome of a dispatch attempt.
+
+    Args:
+        title: Task title for logging context.
+        result: The dispatch result.
+        attempt: Current attempt number (0-indexed).
+        max_retries: Maximum retry attempts allowed.
+    """
+    if result.success:
+        return
+
+    if attempt > 0:
+        logger.info("Retry %d/%d for task %r", attempt, max_retries, title[:60])
+
+    logger.warning(
+        "Dispatch attempt %d failed for task %r: %s",
+        attempt + 1,
+        title[:60],
+        result.error,
+    )
+
+
 async def dispatch_task(
     title: str,
     description: str = "",
@@ -726,17 +800,13 @@ async def dispatch_task(
         if result.success:
             print(f"Assigned to {result.agent.value}")
     """
+    # 1. Validate
+    validation_error = _validate_task(title, task_type, agent, issue_number)
+    if validation_error:
+        return validation_error
+
+    # 2. Resolve task type and agent
     criteria = acceptance_criteria or []
-
-    if not title.strip():
-        return DispatchResult(
-            task_type=task_type or TaskType.ROUTINE_CODING,
-            agent=agent or AgentType.TIMMY,
-            issue_number=issue_number,
-            status=DispatchStatus.FAILED,
-            error="`title` is required.",
-        )
-
     resolved_type = task_type or infer_task_type(title, description)
     resolved_agent = agent or select_agent(resolved_type)
 
@@ -748,18 +818,16 @@ async def dispatch_task(
         issue_number,
     )
 
-    spec = AGENT_REGISTRY[resolved_agent]
-
+    # 3. Select strategy and dispatch with retries
+    strategy = _select_dispatch_strategy(resolved_agent, issue_number)
     last_result: DispatchResult | None = None
-    for attempt in range(max_retries + 1):
-        if attempt > 0:
-            logger.info("Retry %d/%d for task %r", attempt, max_retries, title[:60])
 
-        if spec.interface == "gitea" and issue_number is not None:
+    for attempt in range(max_retries + 1):
+        if strategy == "gitea":
             result = await _dispatch_via_gitea(
                 resolved_agent, issue_number, title, description, criteria
             )
-        elif spec.interface == "api":
+        elif strategy == "api":
             result = await _dispatch_via_api(
                 resolved_agent, title, description, criteria, issue_number, api_endpoint
             )
@@ -772,14 +840,9 @@ async def dispatch_task(
         if result.success:
             return result
 
-        logger.warning(
-            "Dispatch attempt %d failed for task %r: %s",
-            attempt + 1,
-            title[:60],
-            result.error,
-        )
+        _log_dispatch_result(title, result, attempt, max_retries)
 
-    # All attempts exhausted — escalate
+    # 4. All attempts exhausted — escalate
     assert last_result is not None
     last_result.status = DispatchStatus.ESCALATED
     logger.error(