fix(tell): restore outgoing tell routing from the input bar

Input-bar tells went out as a bare "/t" without the target, so the game
rejected them with "you must add the World name". Rebuild the full
"/tell name@world" from the 1.5.6 target chain in a pure BuildOutgoing:

- leg2/leg3 gated on current == Tell so a stale tell target on a Say tab
  can't send a say line silently as /tell (CORR-1)
- world-resolve gate: an unresolvable world falls back to the channel
  prefix, never "/tell name@ text" (COMP-1)
- ResetTempChannel after the send, tell-only

Also clear the runtime tell state on PromoteToPermanent so a promoted tab
can't route a typed line to the old partner, and surface the tell partner
("-> name@world") in the channel pill so a misfire stays visible. Adds
tell-routing and pill-transparency self tests.

HellionChat/Plugin.cs

@@ -387,6 +387,8 @@ public sealed class Plugin : IAsyncDalamudPlugin
                 new SelfTests.MainWindowFlagsStep(this),
                 new SelfTests.SenderNameReformatStep(this),
                 new SelfTests.DisclosureArmStep(this),
+                new SelfTests.TellRoutingBuildStep(this),
+                new SelfTests.TellPillTransparencyStep(this),
             ]);
 
             // Re-surface the wizard for existing users when a major UX