feat(mma): Implement tiered context scoping and add get_definition tool

aggregate.py

@@ -187,6 +187,87 @@ def build_discussion_text(history: list[str]) -> str:
     return "## Discussion History\n\n" + build_discussion_section(history)
 
 
+def build_tier1_context(file_items: list[dict], screenshot_base_dir: Path, screenshots: list[str], history: list[str]) -> str:
+    """
+    Tier 1 Context: Strategic/Orchestration.
+    Full content for core conductor files, summaries for others.
+    """
+    core_files = {"product.md", "tech-stack.md", "workflow.md", "tracks.md"}
+    
+    parts = []
+    
+    # Files section
+    if file_items:
+        sections = []
+        for item in file_items:
+            path = item.get("path")
+            name = path.name if path else ""
+            
+            if name in core_files:
+                # Include in full
+                sections.append("### `" + (item.get("entry") or str(path)) + "`\n\n" + 
+                                f"```{path.suffix.lstrip('.') if path.suffix else 'text'}\n{item.get('content', '')}\n```")
+            else:
+                # Summarize
+                sections.append(summarize.summarise_file(path, item.get("content", "")))
+        
+        parts.append("## Files (Tier 1 - Mixed)\n\n" + "\n\n---\n\n".join(sections))
+
+    if screenshots:
+        parts.append("## Screenshots\n\n" + build_screenshots_section(screenshot_base_dir, screenshots))
+    
+    if history:
+        parts.append("## Discussion History\n\n" + build_discussion_section(history))
+        
+    return "\n\n---\n\n".join(parts)
+
+
+def build_tier2_context(file_items: list[dict], screenshot_base_dir: Path, screenshots: list[str], history: list[str]) -> str:
+    """
+    Tier 2 Context: Architectural/Tech Lead.
+    Full content for all files (standard behavior).
+    """
+    return build_markdown_from_items(file_items, screenshot_base_dir, screenshots, history, summary_only=False)
+
+
+def build_tier3_context(file_items: list[dict], screenshot_base_dir: Path, screenshots: list[str], history: list[str], focus_files: list[str]) -> str:
+    """
+    Tier 3 Context: Execution/Worker.
+    Full content for focus_files, summaries for others.
+    """
+    parts = []
+    
+    if file_items:
+        sections = []
+        for item in file_items:
+            path = item.get("path")
+            entry = item.get("entry", "")
+            path_str = str(path) if path else ""
+            
+            # Check if this file is in focus_files (by name or path)
+            is_focus = False
+            for focus in focus_files:
+                if focus == entry or (path and focus == path.name) or focus in path_str:
+                    is_focus = True
+                    break
+            
+            if is_focus:
+                sections.append("### `" + (entry or path_str) + "`\n\n" + 
+                                f"```{path.suffix.lstrip('.') if path and path.suffix else 'text'}\n{item.get('content', '')}\n```")
+            else:
+                sections.append(summarize.summarise_file(path, item.get("content", "")))
+                
+        parts.append("## Files (Tier 3 - Focused)\n\n" + "\n\n---\n\n".join(sections))
+
+    if screenshots:
+        parts.append("## Screenshots\n\n" + build_screenshots_section(screenshot_base_dir, screenshots))
+    
+    if history:
+        parts.append("## Discussion History\n\n" + build_discussion_section(history))
+        
+    return "\n\n---\n\n".join(parts)
+
+
 def build_markdown(base_dir: Path, files: list[str], screenshot_base_dir: Path, screenshots: list[str], history: list[str], summary_only: bool = False) -> str:
     parts = []
     # STATIC PREFIX: Files and Screenshots must go first to maximize Cache Hits