Add mining turtle for infinite cobblestone generators

New miningTurtle.lua: sits on top of a cobble gen, continuously
digs down, and pushes items into networked chests via wired modem.
Features:
- Configurable mine interval, dump threshold, fuel slot
- Auto-dumps inventory when slots fill or timer expires
- Auto-refuels from designated fuel slot
- Remote reboot via SYSTEM_CHANNEL
- Stats display (mined, dumped, uptime, fuel)
- Persistent config in usr/config/inventory-manager/.miner_config

Also adds:
- startup/miner.lua: auto-update + launch script for standalone use
- .package: new 'Mining Turtle' role (option 4) in setup wizard
- autorun/startup.lua: detects .miner_config and launches miningTurtle

autorun/startup.lua

@@ -26,6 +26,8 @@ elseif cfgExists('.client_config') then
     role = 'client'
 elseif cfgExists('.webbridge_config') then
     role = 'bridge'
+elseif cfgExists('.miner_config') then
+    role = 'miner'
 elseif _G.turtle then
     role = 'turtle'
 end
@@ -69,6 +71,7 @@ local programs = {
     client  = 'inventoryClient.lua',
     bridge  = 'inventoryWebBridge.lua',
     turtle  = 'craftingTurtle.lua',
+    miner   = 'miningTurtle.lua',
 }
 
 local program = fs.combine(BASE, programs[role])