feat(admin): plugin write plane — admin.kick/ban/unban/broadcast

Phase 1 (plugin side) of docs/ADMIN_CONTROLS.md: a staff write plane so the
website can moderate the live shard.

- BridgeAdmin.cs: inbound admin.kick, admin.ban (timed + indefinite),
  admin.unban, admin.broadcast. Each requires an `actor`, refuses targets at
  or above AdminAccessFloor (default CoOwner — Owner-only shield), replies
  admin.ok/admin.error with the reqId echoed, and emits an admin.audit
  (origin=web) broadcast. Attribution is web:<actor> in the console log and
  the ban BanDealer tag. Kicking enumerates NetState.Instances so a
  character-select session is caught too.
- BridgeConfig/Bridge.cfg: AdminWriteEnabled (default OFF — opt-in),
  AdminAccessFloor, broadcast/reason length caps, ban duration clamp.
- tools/stub_sidecar_admin.ps1: live smoke-test harness; *.log gitignored.

Verified: compiles clean against ServUO (0 err/warn); live run on the seeded
shard confirms all four verbs, the audit stream, timed-ban fields, and the
Owner-floor refusal, with no exceptions.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0114TpmrNW4wNXsHq5CR72jQ

tools/stub_sidecar_admin.ps1

@@ -0,0 +1,78 @@
+param(
+    [int] $Port = 7788,
+    [string] $Log = "$PSScriptRoot\sc_admin.log"
+)
+
+# Phase-1 admin write-plane harness. Connects as the sidecar, waits for the shard,
+# fires admin.* commands covering the happy paths and every guard, logs the replies.
+# Requires Bridge.cfg AdminWriteEnabled=true and the seeded world (seed_00x accounts).
+
+function Say($msg) {
+    for ($i = 0; $i -lt 5; $i++) {
+        try { "$msg" | Out-File -FilePath $Log -Append -Encoding utf8; return }
+        catch { Start-Sleep -Milliseconds 100 }
+    }
+}
+
+"" | Out-File -FilePath $Log -Encoding utf8
+Say "[admin] starting on 127.0.0.1:$Port"
+
+$listener = New-Object System.Net.Sockets.TcpListener([System.Net.IPAddress]::Loopback, $Port)
+$listener.Server.SetSocketOption('Socket', 'ReuseAddress', $true)
+
+$bound = $false
+for ($i = 0; $i -lt 30 -and -not $bound; $i++) {
+    try { $listener.Start(); $bound = $true }
+    catch { Start-Sleep -Seconds 1 }
+}
+if (-not $bound) { Say "[admin] could not bind"; exit 1 }
+
+Say "[admin] listening"
+$client = $listener.AcceptTcpClient()
+Say "[admin] === shard connected ==="
+
+$stream = $client.GetStream()
+$reader = New-Object System.IO.StreamReader($stream)
+$writer = New-Object System.IO.StreamWriter($stream)
+$writer.AutoFlush = $true
+
+Start-Sleep -Milliseconds 500
+
+$requests = @(
+    # happy path, no target needed
+    '{"kind":"admin.broadcast","reqId":"a-bcast","actor":"whitlocktech","text":"uo-link admin test broadcast"}',
+    # ban an offline seed account (timed), then unban
+    '{"kind":"admin.ban","reqId":"a-ban","actor":"whitlocktech","account":"seed_001","durationSec":3600,"reason":"harness test"}',
+    '{"kind":"admin.unban","reqId":"a-unban","actor":"whitlocktech","account":"seed_001"}',
+    # kick an offline account -> should succeed with sessions:0
+    '{"kind":"admin.kick","reqId":"a-kick","actor":"whitlocktech","account":"seed_002"}',
+    # floor: whitlocktech is Owner -> must be refused
+    '{"kind":"admin.ban","reqId":"a-floor","actor":"whitlocktech","account":"whitlocktech"}',
+    # unknown target
+    '{"kind":"admin.ban","reqId":"a-unknown","actor":"whitlocktech","account":"does_not_exist"}',
+    # missing actor -> refused by the shared gate
+    '{"kind":"admin.ban","reqId":"a-noactor","account":"seed_003"}'
+)
+
+foreach ($r in $requests) {
+    $writer.WriteLine($r)
+    Say "[admin] -> $r"
+    Start-Sleep -Milliseconds 400
+}
+
+# Drain greedily: block on ReadLine with an idle timeout so a buffered burst is fully read
+# (the DataAvailable-gated pattern drops the tail of a burst that a StreamReader pre-buffers).
+$stream.ReadTimeout = 2500
+try {
+    while ($true) {
+        $line = $reader.ReadLine()
+        if ($null -eq $line) { break }
+        Say "[admin] <- $line"
+    }
+} catch {
+    Say "[admin] read window closed (idle)"
+}
+
+Say "[admin] done"
+$client.Close()
+$listener.Stop()