feat(diff): Add diff rendering helpers for GUI

- Add get_line_color() to classify diff lines
- Add render_diff_text_immediate() for immediate mode rendering
- Add tests for rendering functions

conductor/tracks.md

@@ -26,7 +26,7 @@ This file tracks all major tracks for the project. Each track has its own detail
 3. [x] **Track: Visual DAG & Interactive Ticket Editing**
    *Link: [./tracks/visual_dag_ticket_editing_20260306/](./tracks/visual_dag_ticket_editing_20260306/)*
 
-4. [ ] **Track: Advanced Tier 4 QA Auto-Patching**
+4. [~] **Track: Advanced Tier 4 QA Auto-Patching**
    *Link: [./tracks/tier4_auto_patching_20260306/](./tracks/tier4_auto_patching_20260306/)*
 
 5. [ ] **Track: Transitioning to Native Orchestrator**

src/diff_viewer.py

@@ -127,3 +127,23 @@ def format_diff_for_display(diff_files: List[DiffFile]) -> str:
       for line in hunk.lines:
         output.append(f"    {line}")
   return "\n".join(output)
+
+def get_line_color(line: str) -> Optional[str]:
+  if line.startswith("+"):
+    return "green"
+  elif line.startswith("-"):
+    return "red"
+  elif line.startswith("@@"):
+    return "cyan"
+  return None
+
+def render_diff_text_immediate(diff_files: List[DiffFile]) -> List[tuple[str, Optional[str]]]:
+  output: List[tuple[str, Optional[str]]] = []
+  for df in diff_files:
+    output.append((f"File: {df.old_path}", "white"))
+    for hunk in df.hunks:
+      output.append((hunk.header, "cyan"))
+      for line in hunk.lines:
+        color = get_line_color(line)
+        output.append((line, color))
+  return output

tests/test_diff_viewer.py

@@ -1,5 +1,5 @@
 import pytest
-from src.diff_viewer import parse_diff, DiffFile, DiffHunk, parse_hunk_header
+from src.diff_viewer import parse_diff, DiffFile, DiffHunk, parse_hunk_header, get_line_color, render_diff_text_immediate
 
 def test_parse_diff_empty() -> None:
   result = parse_diff("")
@@ -81,3 +81,24 @@ def test_diff_line_classification() -> None:
   assert any(line.startswith("-") for line in hunk.lines)
   assert any(line.startswith("+") for line in hunk.lines)
   assert any(line.startswith(" ") or not line.startswith(("-", "+")) for line in hunk.lines)
+
+def test_get_line_color() -> None:
+  assert get_line_color("+added") == "green"
+  assert get_line_color("-removed") == "red"
+  assert get_line_color("@@ -1,3 +1,4 @@") == "cyan"
+  assert get_line_color(" context") == None
+
+def test_render_diff_text_immediate() -> None:
+  diff_text = """--- a/test.py
++++ b/test.py
+@@ -1 +1 @@
+-old
++new"""
+  diff_files = parse_diff(diff_text)
+  output = render_diff_text_immediate(diff_files)
+  
+  assert len(output) > 0
+  assert ("File: test.py", "white") in output
+  assert ("@@ -1 +1 @@", "cyan") in output
+  assert ("-old", "red") in output
+  assert ("+new", "green") in output