agent: default unset scope to global (safe by default)

Only tools that explicitly declare scope="write" get path-based
parallelism. Unset scope is now global (full barrier), avoiding the
"path is a lie" problem where a tool has a path arg but modifies
other files (e.g., lsp_rename).

Tools must opt in to parallelism:
- scope=read: never conflicts
- scope=write: conflicts on same path only
- scope=global (or unset): serialization barrier

Added scope=write to file_edit.meta and file_write.meta.

cmd/olliesrv/internal/agent/loop.go

@@ -417,22 +417,21 @@ func execToolCalls(rt *Runtime, ctx TurnCtx, toolCalls []backend.ToolCall, resul
 const conflictKeyGlobal = "\x00GLOBAL"
 
 // toolConflictKeys returns the set of resource keys a tool call touches.
-// Scope "read" tools return nil (never conflict). Scope "global" tools
-// return the global sentinel. Scope "write" (or empty) tools return their
-// file path, or global if no path is detectable.
+// Scope "read" tools return nil (never conflict). Scope "write" tools
+// return their file path (or global if no path detectable). Everything
+// else (scope "global" or unset) is a full serialization barrier.
 func toolConflictKeys(rt *Runtime, call backend.ToolCall) []string {
 	scope := rt.ToolMeta[call.Name].Scope
 	if scope == "read" {
 		return nil // reads never conflict
 	}
-	if scope == "global" {
+	if scope == "write" {
+		if p := extractFilePath(call.Arguments); p != "" {
+			return []string{p}
+		}
 		return []string{conflictKeyGlobal}
 	}
-	// "write" or unset: infer from path argument
-	if p := extractFilePath(call.Arguments); p != "" {
-		return []string{p}
-	}
-	// No detectable path: global barrier
+	// "global", empty, or anything else: full barrier
 	return []string{conflictKeyGlobal}
 }
 

data/tools/file_edit.meta

@@ -2,7 +2,7 @@
   "description": "Replace text in a file. Has fuzzy matching (whitespace/indent flexible).",
   "outputFormat": "diff",
   "resetsCounter": true,
-  "prompt": "## file_edit\n\nReplace text in a file. Has fuzzy matching (whitespace/indent flexible).\n\n**Args**: `path`, `old_string`, `new_string` (required); `replace_all` (optional)\n\n```\nfile_edit(path=\"/abs/path\", old_string=\"old text\", new_string=\"new text\")\nfile_edit(path=\"/abs/path\", old_string=\"old text\", new_string=\"new text\", replace_all=\"true\")\n```\n\n**Constraints**: Absolute paths only. Errors if `old_string` matches multiple locations — add surrounding context to disambiguate, or use `replace_all=true`.",
+  "prompt": "## file_edit\n\nReplace text in a file. Has fuzzy matching (whitespace/indent flexible).\n\n**Args**: `path`, `old_string`, `new_string` (required); `replace_all` (optional)\n\n```\nfile_edit(path=\"/abs/path\", old_string=\"old text\", new_string=\"new text\")\nfile_edit(path=\"/abs/path\", old_string=\"old text\", new_string=\"new text\", replace_all=\"true\")\n```\n\n**Constraints**: Absolute paths only. Errors if `old_string` matches multiple locations \u2014 add surrounding context to disambiguate, or use `replace_all=true`.",
   "args": {
     "type": "object",
     "required": [
@@ -28,5 +28,6 @@
         "description": "Set to true/1/yes to replace all occurrences"
       }
     }
-  }
+  },
+  "scope": "write"
 }

data/tools/file_write.meta

@@ -19,5 +19,6 @@
         "description": "File content to write"
       }
     }
-  }
+  },
+  "scope": "write"
 }