fix(chat): block / unknown commands from broadcasting as speech

User reported typing /ls (a command-style request, not chat) gets
echoed by the server as "You say, \"/ls\"". Slash-prefix is a
COMMAND surface, never a chat surface. Filed after the same flow
that produced @help and the welcome-message work.

Behavior change at the ChatPanel submit layer:
- Any /-prefixed input whose verb isn't in our alias tables now
  renders a local "[System] Unknown command: /foo. Type /help for
  the list." line and is NEVER published to the bus. No SendChatCmd,
  no Talk packet. The server never sees /foo.
- Known /-verbs (/say /tell /reply /retell /general /allegiance
  /patron /vassals /monarch /covassals /fellowship /lookingforgroup
  /trade /roleplay /society /olthoi /help /clear /framerate /loc
  and friends) still flow through ChatInputParser.Parse → SendChatCmd
  exactly as before.
- @-prefix unchanged: ACE's CommandManager handles unknown @ verbs
  server-side and replies via SystemChat ("Unknown command: foo")
  per ACE GameActionTalk.cs:21. Our @ -> / normalization for known
  verbs (Phase J Tier 1) and the @-passthrough fallthrough for
  unknown verbs both still apply.

ChatInputParser now exposes:
- IsKnownVerb(string verb): query against the union of every alias
  table. Used by ChatPanel to discriminate "unknown verb" from
  "known verb with bad args".
- GetVerbToken(string command): public alias of the existing
  ExtractVerb so callers can pull the first whitespace token without
  reproducing the helper.

Parse itself is unchanged — its existing fall-through (Say with
literal text) still applies for unknown /-verbs called directly via
the parser, but ChatPanel intercepts before reaching that path so
the fall-through never fires through the live submit pipeline. Tests
that directly call Parse continue to pass; the new ChatPanel-level
tests pin the unknown-command rejection.

19 new tests:
- ChatInputParserTests: 10 IsKnownVerb Theory cases + 4 GetVerbToken
  Theory cases.
- ChatPanelInputTests: 5 Theory cases for Submit_UnknownSlashCommand
  covering /foo, /ls, /mp <path>, /genio, and bare /.

Solution total: 1086 green (243 Core.Net + 183 UI + 660 Core),
0 warnings.

Acceptance: type /ls, /mp /path, /anything-not-known — see local
"[System] Unknown command: /xxx. Type /help for the list of
supported commands." Nothing reaches the wire.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/AcDream.UI.Abstractions.Tests/Panels/Chat/ChatInputParserTests.cs

@@ -228,8 +228,11 @@ public sealed class ChatInputParserTests
         // Phase J added long-form aliases (/general, /allegiance,
         // /patron, etc.). The exact-token rule still applies — a
         // verb prefix that ISN'T one of the listed aliases falls
-        // through to the default channel. "/genio" is not /g, /general,
-        // or /gen — must stay as Say carrying the literal text.
+        // through. The Parse-level behaviour for unknown /-verbs is
+        // still "Say with the literal text" (matches holtburger);
+        // the ChatPanel layer is what catches unknowns and shows the
+        // local "Unknown command" line. ChatPanelInputTests cover
+        // that end-to-end behaviour.
         var parsed = ChatInputParser.Parse("/genio public", ChatChannelKind.Say, lastTellSender: null);
 
         Assert.NotNull(parsed);
@@ -237,6 +240,32 @@ public sealed class ChatInputParserTests
         Assert.Equal("/genio public", parsed.Value.Text);
     }
 
+    [Theory]
+    [InlineData("/g",          true)]
+    [InlineData("/say",        true)]
+    [InlineData("/tell",       true)]
+    [InlineData("/retell",     true)]
+    [InlineData("/allegiance", true)]
+    [InlineData("/lookingforgroup", true)]
+    [InlineData("/genio",      false)]
+    [InlineData("/ls",         false)]
+    [InlineData("/foo",        false)]
+    [InlineData("/",           false)]
+    public void IsKnownVerb_ChecksAgainstAliasTables(string verb, bool expected)
+    {
+        Assert.Equal(expected, ChatInputParser.IsKnownVerb(verb));
+    }
+
+    [Theory]
+    [InlineData("/g hello", "/g")]
+    [InlineData("/tell Bob hi", "/tell")]
+    [InlineData("/foo", "/foo")]
+    [InlineData("/", "/")]
+    public void GetVerbToken_PullsFirstWhitespaceToken(string command, string expected)
+    {
+        Assert.Equal(expected, ChatInputParser.GetVerbToken(command));
+    }
+
     [Theory]
     [InlineData("/general what's the deal",     ChatChannelKind.General,    "what's the deal")]
     [InlineData("/allegiance recall",            ChatChannelKind.Allegiance, "recall")]