feat(agent): honor per-agent tools.rate_limit_per_hour (#1263)

The agent config UI (tools-profile-section) and i18n already expose a
per-agent "Rate Limit (per hour)" field saved into tools_config, but the
backend ignored it — the tool rate limiter only ever used the global
tools.rate_limit_per_hour. Wire the field through: ToolPolicySpec gains
RateLimitPerHour; the agent loop threads it into the tool-execution
context; the registry passes it to the limiter, which uses it in place
of the global max when > 0 (0 inherits the global).

internal/agent/loop_context.go

@@ -113,6 +113,9 @@ func (l *Loop) injectContext(ctx context.Context, req *RunRequest) (contextSetup
 		waitToolCfg = l.agentToolPolicy.Wait
 		ctx = tools.WithWaitToolConfig(ctx, waitToolCfg)
 	}
+	if l.agentToolPolicy != nil && l.agentToolPolicy.RateLimitPerHour > 0 {
+		ctx = tools.WithToolRateLimitOverride(ctx, l.agentToolPolicy.RateLimitPerHour)
+	}
 	if l.sandboxCfg != nil {
 		ctx = tools.WithSandboxConfig(ctx, l.sandboxCfg)
 	}