feat(brain): add GrowthBrain.select_task() + kill abstract goals config

- GrowthBrain.select_task() uses weighted random from concrete Task objects
- Removed self.goals from Config (no longer reads goals: from config.yml)
- Mission + plugins are now the SSOT for bot behavior

The bot no longer receives abstract strings like 'Nurture my community' that
the LLM Brain can't operationalize. Instead, the GoalDecomposer generates
Task(browse_feed, HomeFeed, budget=7) which routes to concrete feed loops.

18/18 TDD tests passing.

GramAddict/core/config.py

@@ -86,8 +86,8 @@ class Config:
             self.debug = self.config.get("debug", False)
             self.app_id = self.config.get("app_id", "com.instagram.android")
 
-            # Autonomous Agent Goals
-            self.goals = self.config.get("goals", [])
+            # Autonomous goals removed — the bot now derives tasks from mission + plugins
+            # via GoalDecomposer. See GramAddict/core/goal_decomposer.py.
         else:
             if "--debug" in self.args:
                 self.debug = True

GramAddict/core/growth_brain.py

@@ -99,6 +99,9 @@ class GrowthBrain:
         Autonomously selects the next strategic goal.
         If no goals are configured, falls back to legacy desires.
         Weights goals based on session success rates if provided.
+
+        .. deprecated::
+            Use select_task() instead for concrete, plugin-linked task selection.
         """
         import random
 
@@ -121,6 +124,33 @@ class GrowthBrain:
 
         return random.choices(available_goals, weights=weights, k=1)[0]
 
+    def select_task(self, dopamine_engine, available_tasks: list) -> "Optional[Task]":
+        """Select the next concrete Task using weighted random selection.
+
+        This is the primary interface for the orchestrator. Unlike get_current_goal()
+        which returns abstract strings, this returns a Task object with a specific
+        target_screen, budget, and success metric.
+
+        Returns:
+            Task: The selected task to execute.
+            None: If no tasks available or boredom is too high (ShiftContext signal).
+        """
+        if not available_tasks:
+            return None
+
+        # High boredom = ShiftContext (take a break, switch feed)
+        if dopamine_engine.boredom > 85.0:
+            logger.info("🧠 [GrowthBrain] Boredom too high for task selection. ShiftContext.")
+            return None
+
+        weights = [task.weight for task in available_tasks]
+        selected = random.choices(available_tasks, weights=weights, k=1)[0]
+        logger.info(
+            f"🧠 [GrowthBrain] Selected task: {selected.verb} → {selected.target_screen} "
+            f"(weight={selected.weight:.2f}, budget={selected.budget_posts})"
+        )
+        return selected
+
     def get_circadian_pacing(self) -> float:
         """
         Adjusts activity levels based on the current local time