style: fix lint across client packages

eslint --fix autofixes plus manual repairs: max-len line splits
(fake-api handlers, notifier/slots JSDoc, spec signatures), charAt over
non-null-asserted indexing in slash detect/menu cores, Array.from for
code-point capping, typeof assertions for unbound-method in specs,
generic getByRole for the send-button cast, effect disposer void-wrap in
command register, and dropped unused type imports.

apps/web/tests/slash-flow.snapshot.ts

@@ -122,7 +122,7 @@ it('locked view state, connectWorkspace unlock, /echo claim chain, and blank-on-
   // workspace picker is live.
   const locked = await screen.findByPlaceholderText(
     'Choose a workspace to start', {}, { timeout: 10_000 },
-  ) as HTMLTextAreaElement
+  )
   expect(locked.disabled).toBe(true)
 
   // Pick (create) a Workspace: connectWorkspace materializes the full
@@ -139,7 +139,7 @@ it('locked view state, connectWorkspace unlock, /echo claim chain, and blank-on-
 
   const composer = await screen.findByPlaceholderText(
     'Describe what you want to build', {}, { timeout: 10_000 },
-  ) as HTMLTextAreaElement
+  )
   expect(composer.disabled).toBe(false)
 
   // '/' opens the menu with the session's wire command catalog (the session

apps/web/tests/workspace-flow.snapshot.ts

@@ -117,14 +117,14 @@ function workspaceChip(): HTMLElement {
 async function findLockedComposer(): Promise<HTMLTextAreaElement> {
   return await screen.findByPlaceholderText(
     'Choose a workspace to start', {}, { timeout: 10_000 },
-  ) as HTMLTextAreaElement
+  )
 }
 
 /** The live blank-session hero composer (session materialized). */
 async function findHeroComposer(): Promise<HTMLTextAreaElement> {
   return await screen.findByPlaceholderText(
     'Describe what you want to build', {}, { timeout: 10_000 },
-  ) as HTMLTextAreaElement
+  )
 }
 
 /** Edit the machine-owned controlled input and assert the same-tick echo. */
@@ -161,7 +161,7 @@ it('locks the composer in the New Session view state until a Workspace is chosen
     headline: visibleText(screen.getByText("Let's start building")),
     chip: visibleText(workspaceChip()),
     composerDisabled: composer.disabled,
-    sendDisabled: (screen.getByRole('button', { name: 'Send message' }) as HTMLButtonElement).disabled,
+    sendDisabled: screen.getByRole<HTMLButtonElement>('button', { name: 'Send message' }).disabled,
     sidebar: visibleText(tree),
   }).toMatchInlineSnapshot(`
     {