Rename gh-implement to implement-issue and implement to implement-plan

Gives both workflows clearer, consistent names. Updates the graph
identifiers and the child_workflow reference accordingly.

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

fabro/workflows/implement-issue/workflow.fabro

@@ -1,4 +1,4 @@
-digraph GhImplement {
+digraph ImplementIssue {
     graph [
         goal="Implement a GitHub issue",
         model_stylesheet="
@@ -12,7 +12,7 @@ digraph GhImplement {
 
     plan [label="Plan", prompt="Fetch the GitHub issue from the goal using: gh issue view $goal --json title,body,labels,comments\n\nRead the issue title, description, and any comments carefully. Analyze what code changes are needed to resolve the issue.\n\nWrite a detailed implementation plan to plan.md that includes:\n- Summary of the issue\n- Files to create or modify\n- Step-by-step implementation approach\n- Test cases to add or update\n\nThe plan should be specific enough for another agent to implement without seeing the original issue.\n\nRespond with the location of the plan file (plan.md)."]
 
-    implement [label="Implement", shape=house, stack.child_workflow="fabro/workflows/implement/workflow.fabro", manager.max_cycles=100]
+    implement [label="Implement", shape=house, stack.child_workflow="fabro/workflows/implement-plan/workflow.fabro", manager.max_cycles=100]
 
     start -> plan
     plan -> implement [fidelity="summary:high"]

fabro/workflows/implement-plan/workflow.fabro

@@ -1,4 +1,4 @@
-digraph ImplementAndSimplify {
+digraph ImplementPlan {
     graph [
         goal="Implement and simplify",
         model_stylesheet="