Goal completion is a claim, not a decision: the independent audit

Adopted from studying Claude Code's /goal (completion judged by a fresh
model, never the one doing the work) and pi-goal-x's auditor (isolated
session, read-only tools, explicit approval marker, rejects scaffold-only
and proxy-metric completions).

complete_goal no longer closes a goal on the caller's word:
- It now takes a required `evidence` claim, and permission/argument gates
  run before any audit spend.
- The audit is an isolated tool-turn loop: fresh conversation (the auditor
  never sees the executor's transcript), read-only workspace tools (no
  run_command), strict auditor instructions, at most 6 iterations.
- Only an explicit <approved/> closes the goal (recorded with the audit
  verdict). <disapproved/>, no marker, or an exhausted budget all leave the
  goal active and hand the decisive gap back to the caller as the tool
  result.
- The handler moved from the sync dispatcher into the run loop's async
  routing because it needs provider access; the goal-review prompt warns
  that substanceless claims will bounce.

AGENTS.md documents both this and the web-access contract.

src/main/services/agent-tools.ts

@@ -8,7 +8,7 @@ import { readMessagesTool } from "./agent-read-messages";
 import { grantConnectorTool, listConnectorsTool } from "./agent-connector-tools";
 import { bindSkillSlugs, grantSkillTool, listSkillsTool } from "./agent-skill-tools";
 import { createDocumentTool, writeDeliverableTool } from "./agent-deliverable-tools";
-import { completeGoalTool, GOAL_TOOLS } from "./agent-goal-tools";
+import { GOAL_TOOLS } from "./agent-goal-tools";
 import { describeSend } from "./agent-message-presence";
 import { optionalString, optionalStringArray, requireString } from "./agent-tool-args";
 import type { JsonRecord } from "./provider-http";
@@ -234,8 +234,6 @@ export function dispatchAgentTool(
         return createTask(deps, ctx, call.arguments, options);
       case "update_task_status":
         return updateTaskStatus(deps, ctx, call.arguments);
-      case "complete_goal":
-        return completeGoalTool(deps, ctx);
       case "write_deliverable":
         return writeDeliverableTool(deps, ctx, call.arguments);
       case "send_message":