feat(harness): authority, turn contract, tools, clean_agent_preview

Chat/agent harness work: request-authority model, turn contract, tool
policy/parsing/execution, clean_agent_preview streaming/thinking, ask_user
persistence, session probes, and scheduler.

Source: vendor/photocraft (ad1cff44) harness files, 3-way merged onto
upstream/dev (a8c147b2). Harness core files were independently developed
in both lineages; resolution policy documented in pr_work/C_conflicts.md
(vendor kept where ahead, upstream kept where vendor is behind; full delta
preserved in pr_work/C_upstream_delta.patch).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/agent_tools/__init__.py

@@ -29,6 +29,7 @@ from .interaction_tools import AskUserTool, UpdatePlanTool
 from .model_interaction_tools import ChatWithModelTool, AskTeacherTool, ListModelsTool
 from .bg_job_tools import ManageBgJobsTool
 from .session_tools import CreateSessionTool, ListSessionsTool, SendToSessionTool, ManageSessionTool
+from .editor_tools import PlanEditTool, RunEditorCommandTool, GetEditorScreenshotTool, AiEditImageTool
 from .admin_tools import (
     ADMIN_TOOL_HANDLERS,
     do_manage_endpoints, do_manage_mcp, do_manage_webhooks,
@@ -72,6 +73,10 @@ TOOL_HANDLERS = {
     "list_sessions": ListSessionsTool().execute,
     "send_to_session": SendToSessionTool().execute,
     "manage_session": ManageSessionTool().execute,
+    "plan_edit": PlanEditTool().execute,
+    "run_editor_command": RunEditorCommandTool().execute,
+    "get_editor_screenshot": GetEditorScreenshotTool().execute,
+    "ai_edit_image": AiEditImageTool().execute,
 }
 # Config/integration admin tools (manage_endpoints/mcp/webhooks/tokens/settings).
 TOOL_HANDLERS.update(ADMIN_TOOL_HANDLERS)

src/agent_tools/document_tools.py

@@ -496,6 +496,7 @@ def _create_pdf_text_derivative(db, *, source_doc, content: str, owner: Optional
         "content": clean,
         "version": 1,
         "source_doc_id": getattr(source_doc, "id", None),
+        "exit_code": 0,
     }
 
 
@@ -618,6 +619,7 @@ class CreateDocumentTool:
                 "language": language,
                 "content": content,
                 "version": 1,
+                "exit_code": 0,
             }
         except Exception as e:
             db.rollback()
@@ -708,6 +710,7 @@ class UpdateDocumentTool:
                 "language": doc.language,
                 "content": new_content,
                 "version": new_ver,
+                "exit_code": 0,
             }
         except Exception as e:
             db.rollback()
@@ -863,6 +866,7 @@ class EditDocumentTool:
                         "version": new_ver,
                         "applied": applied,
                         "skipped": skipped,
+                        "exit_code": 0,
                     }
                 return {"error": "No edits applied — FIND text cannot be blank"}
 
@@ -968,6 +972,7 @@ class EditDocumentTool:
                 "version": new_ver,
                 "applied": applied,
                 "skipped": skipped,
+                "exit_code": 0,
             }
             if partial_edits:
                 result.update({
@@ -1059,6 +1064,7 @@ class SuggestDocumentTool:
                 "partial": bool(invalid),
                 "rejected": len(invalid),
                 "invalid_suggestions": invalid,
+                "exit_code": 0,
             }
         finally:
             db.close()

src/agent_tools/web_tools.py

@@ -14,6 +14,7 @@ import tempfile
 import time
 import html
 import hashlib
+import pwd
 import urllib.parse
 import urllib.request
 import uuid
@@ -31,7 +32,10 @@ _ACTIVE_BROWSER_SESSIONS: set[str] = set()
 def _service_home() -> Path:
     """Return the account home even when a task overrides ``HOME``."""
 
-    return platform_compat.service_home()
+    try:
+        return Path(pwd.getpwuid(os.getuid()).pw_dir)
+    except (KeyError, OSError):
+        return Path.home()
 
 
 def _host_npm_roots() -> list[Path]: