Add executor tool loop (A12/A15) — step 5b

- tools.py: four flat tools (read_file, write_file, list_dir,
  run_command) per A15's reduced manifest. Deliberately unsandboxed:
  the VM is the trust boundary (B3) and tool use is auto-approved
  inside an approved unit of work (A4), so path confinement would add
  failure modes without adding safety. What is enforced is
  operational — timeout with process-group kill so a backgrounded
  server cannot outlive its command, output truncation so a build log
  cannot eat the context window, closed stdin so prompts fail fast,
  and a scrubbed environment so project code never sees the agent's
  credentials
- executor.py: renders the log, calls the executor role with the
  reduced manifest, dispatches tool calls, and checkpoints every
  result (A13). Escalation is observable, never self-assessed (A12):
  consecutive command failures and a hard turn cap. Failed reads do
  not count — looking around is not failing
- Until delegation exists (step 7), escalation gates to the human
  with the failures attached
- control.py: start milestone now runs the executor; a stopped
  milestone gates to AWAIT_INPUT

Two bugs found by running it live against real models:

- A turn-ending gate tool (submit_plan) left a tool_call with no
  tool_result, which providers reject outright, so every planning
  turn after the first failed with a 400. The planner now records the
  gate as the call's outcome, which is also the truthful transcript
- The renderer now emits a placeholder for any tool_call lacking a
  result, so a crash between call and result (A3) cannot poison the
  transcript permanently

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

nisse-dev/src/nisse_dev/planner.py

@@ -11,7 +11,7 @@ crash mid-planning leaves a truthful transcript.
 
 from typing import Any
 
-from nisse_dev.canonical import AssistantText, ToolCall
+from nisse_dev.canonical import AssistantText, ToolCall, ToolResult
 from nisse_dev.control import AskHuman, PlanningError, SubmitPlan
 from nisse_dev.llm import LLMClient, LLMError, RoleMap
 from nisse_dev.state import StateStore
@@ -142,6 +142,21 @@ class LLMPlanningAgent:
                 continue
             if isinstance(event, ToolCall):
                 action = self._interpret(event)
+                if action is not None:
+                    # The gate is this call's outcome. Recording it keeps the
+                    # transcript renderable: providers reject a tool call with
+                    # no result, and the next planning turn replays this log.
+                    self._store.append_event(
+                        ToolResult(
+                            call_id=event.call_id,
+                            result=(
+                                "plan posted for approval; turn ended"
+                                if isinstance(action, SubmitPlan)
+                                else "question posted; awaiting the operator"
+                            ),
+                            success=True,
+                        )
+                    )
         return action
 
     def _interpret(self, call: ToolCall) -> SubmitPlan | AskHuman | None: