T6: expand telemetry to T5-parity reports and add .join module

- Telemetry: async queued game_start/heartbeat/round_change/game_end with
  sequenced FIFO, watchdog, log-level dvar, and per-player stats snapshot
- Join: new tws_t6_join.gsc chat command lets late spectators enter mid-match
- Update NOTES/README/check.ps1 to reflect the six-module layout

t6/tools/check.ps1

@@ -6,7 +6,7 @@ $ErrorActionPreference = 'Stop'
 $compiler = (Resolve-Path -LiteralPath $CompilerPath).Path
 $repo = Split-Path -Parent $PSScriptRoot
 $files = @(Get-ChildItem -LiteralPath $repo -Filter 'tws_t6_*.gsc' | Sort-Object Name)
-if ($files.Count -ne 5) { throw 'Expected the five TWS modules: common, HUD, AFK, lock, telemetry.' }
+if ($files.Count -ne 6) { throw 'Expected the six TWS modules: common, HUD, AFK, lock, telemetry, join.' }
 $common = Get-Content -LiteralPath (Join-Path $repo 'tws_t6_common.gsc') -Raw
 $functions = @([regex]::Matches($common, '(?m)^([a-zA-Z_][a-zA-Z_0-9]*)\([^\r\n]*\)\s*\r?\n\{') | ForEach-Object { $_.Groups[1].Value })
 foreach ($file in $files) {
@@ -31,4 +31,4 @@ foreach ($file in $files) {
     }
     Write-Output "PASS $($file.Name)"
 }
-Write-Output 'All five T6 compile checks and common references passed. Runtime linking/gameplay require Plutonium.'
+Write-Output 'All six T6 compile checks and common references passed. Runtime linking/gameplay require Plutonium.'