fix(tui): lowercase slash command names once at dispatch

Case-insensitive routing matched /CLEAR but forwarded the typed case, so
the exact registry lookup missed and reported Unknown command. The router
now returns the canonical lowercase id; the ignores-case test asserts the
lowered name and a keeper test drives /CLEAR through the real registry.

Author: TheGreatAxios

src/tui/runner/submit.ts

@@ -91,6 +91,11 @@ function hasKnownCommand(known: KnownCommandNames, name: string): boolean {
  * stays empty. Callers that omit `knownCommands` (tests and non-registry
  * surfaces) keep the legacy any-leading-slash-is-a-command rule; every
  * product call site passes the registry set.
+ *
+ * Case is lowered once here: the returned command name is the canonical
+ * lowercase registry id, so the downstream exact-`Map.get` lookup
+ * (`getCommand`) hits for mixed-case input like `/CLEAR`. Matching stays
+ * case-insensitive via `hasKnownCommand`.
  */
 export function routeSubmission(
   raw: string,
@@ -107,7 +112,7 @@ export function routeSubmission(
   if (knownCommands !== undefined && !hasKnownCommand(knownCommands, name)) {
     return { kind: "prompt", text: trimmed };
   }
-  return { kind: "command", name, args };
+  return { kind: "command", name: name.toLowerCase(), args };
 }
 
 export interface SubmitHandlerDeps {

src/tui/submit-handler.test.ts

@@ -21,6 +21,8 @@ import {
   isFeedbackCapturePending,
   resetFeedbackStateForTests,
 } from "../telemetry/feedback.js";
+import { registerBuiltInCommands } from "./commands/built-in.js";
+import { getCommand, listCommands } from "./commands/registry.js";
 
 afterEach(() => {
   resetFeedbackStateForTests();
@@ -124,10 +126,30 @@ describe("composer submit handler", () => {
   test("command matching ignores case", () => {
     const h = harness();
     expect(h.submit("/CLEAR")).toBe("local");
-    expect(h.dispatched).toEqual([{ name: "CLEAR", args: "" }]);
+    expect(h.dispatched).toEqual([{ name: "clear", args: "" }]);
     expect(h.prompts).toEqual([]);
   });
 
+  test("/CLEAR dispatches clear through the real registry", () => {
+    registerBuiltInCommands();
+    const dispatched: Dispatched[] = [];
+    const resolved: (string | undefined)[] = [];
+    const submit = createSubmitHandler({
+      dispatchCommand: (name, args) => {
+        dispatched.push({ name, args });
+        resolved.push(getCommand(name)?.name);
+      },
+      sendPrompt: () => {
+        throw new Error("/CLEAR must dispatch, not prompt");
+      },
+      onPromptSubmitted: () => undefined,
+      knownCommands: () => listCommands().map((c) => c.name),
+    });
+    expect(submit("/CLEAR")).toBe("local");
+    expect(dispatched).toEqual([{ name: "clear", args: "" }]);
+    expect(resolved).toEqual(["clear"]);
+  });
+
   test("a leading-slash path is captured as feedback while armed", () => {
     const feedbackTexts: string[] = [];
     const h = harness({