feat: agent loop harness with Claude Code plugin support

Generator-evaluator architecture with iterative context-reset for
long-running coding tasks. Ships as a Claude Code plugin — install
with /plugin and use /agent-loop:init, /agent-loop:plan, /agent-loop:run.

config.json.example

@@ -0,0 +1,26 @@
+{
+  "tool": "claude",
+  "mode": "implement",
+  "maxIterations": 20,
+  "skipEval": false,
+  "evalRetries": 2,
+  "autoHooks": true,
+  "branchPrefix": "loop/",
+  "scopeBudgets": {
+    "explore": {
+      "maxFilesToRead": 15,
+      "maxLinesToWrite": 0,
+      "maxFilesToModify": 0
+    },
+    "implement": {
+      "maxFilesToRead": 50,
+      "maxLinesToWrite": 500,
+      "maxFilesToModify": 10
+    },
+    "fix": {
+      "maxFilesToRead": 30,
+      "maxLinesToWrite": 200,
+      "maxFilesToModify": 5
+    }
+  }
+}