Rmarkdown build (index.html) in SublimeText 3 not displaying leaflet map, but `rmarkdown::run()` works

First Attempt with SublimeText 3 R Markdown Build

If I build with R Markdown in SublimeText 3, an index.html file is generated. If I then open this .html file in either Firefox, Chrome, Brave, etc, the map does not render. For example:

Result

Second Attempt with Terminal

However, If I switch to my Windows terminal and load R, then use rmarkdown::run(), the map generates in either browser of choice. For instance:

Result

Reprex Code: flexdashboard with shiny integration

---
title: "COVID-19 Tracker"
date: "`r Sys.Date()`"
fontsize: 9pt
fontfamily: Segoe UI
output: flexdashboard::flex_dashboard
runtime: shiny
---

suppressMessages( require(dplyr) )
suppressMessages( require(tidyr) )
suppressMessages( require(flexdashboard) )
suppressMessages( require(leaflet) )
suppressMessages( require(maps) )
suppressMessages( require(mapdata) )
suppressMessages( require(shiny) )
suppressMessages( require(htmltools) )
suppressMessages( require(htmlwidgets) )

cntry <- map("world2Hires",fill=F,plot=F)$names[1:100]
cntry <- cntry[order(cntry)]
getBounds <- function(vec=NULL)
{
    lng1 <- rep(0,length(vec))
    lat1 <- rep(0,length(vec))
    lng2 <- rep(0,length(vec))
    lat2 <- rep(0,length(vec))
    for (i in 1:length(vec))
    {
        lat1[i] <- map("world2Hires",fill=F,region=vec[i],plot=F)$range[3] %>% round(5)
        lng2[i] <- map("world2Hires",fill=F,region=vec[i],plot=F)$range[2] %>% round(5)
        lat2[i] <- map("world2Hires",fill=F,region=vec[i],plot=F)$range[4] %>% round(5)
        lng2[i] <- map("world2Hires",fill=F,region=vec[i],plot=F)$range[1] %>% round(5)
    }
    cbind(lng1,lat1,lng2,lat2)
}

location <- getBounds(vec=cntry)
df1 <- data.frame(cntry,location)

Column {.sidebar}
--------------------------------------------------

### Epicenter Region

# https://community.rstudio.com/t/rstudio-connect-interactive-markdown-with-shiny-error-path-for-html-dependency-not-provided/7263/11
selectInput("loc",
        label="Select Region:",
        selectize=FALSE,        
        choices=df1[,1],
        selected=df1[19,1])

Column
--------------------------------------------------

### COVID-19 Epicenters

renderLeaflet({
    leaflet() %>% addTiles() %>%
    # add tile theme layer
    addProviderTiles(providers$CartoDB.Positron) %>%
    # add bounds
    fitBounds(lng1=map("world2Hires",fill=F,region=input$loc,plot=F)$range[1],
          lat1=map("world2Hires",fill=F,region=input$loc,plot=F)$range[3],
          lng2=map("world2Hires",fill=F,region=input$loc,plot=F)$range[2],
          lat2=map("world2Hires",fill=F,region=input$loc,plot=F)$range[4])
})