feat(native-chat): show the reported argument hint in the slash picker

`argumentHint` was carried to the renderer but nothing read it. Show it
beside the command token — `/goal <objective>` over the description — so a
row says how the command is invoked, not just what it does.

It sits at the row's existing 11px muted tier, subordinate to the
description, and truncates in a min-width-0 flex row; the picker also caps
the hint at 80 characters, so a provider cannot swamp the row.

src/renderer/src/components/native-chat/NativeChatAutocompleteMenus.test.tsx

@@ -3,6 +3,8 @@
 import { cleanup, fireEvent, render, screen } from '@testing-library/react'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import { NativeChatPickerMenu } from './NativeChatAutocompleteMenus'
+import { buildNativeChatPickerItems } from './native-chat-picker-items'
+import { sessionSlashCommandSuggestions } from '../../../../shared/native-chat-slash-commands'
 import type { ComposerAutocomplete } from './native-chat-composer-state'
 
 function autocomplete(
@@ -128,6 +130,45 @@ describe('NativeChatPickerMenu', () => {
     expect(screen.getAllByText('No matching commands')).toHaveLength(2)
   })
 
+  it('shows the argument hint the provider reported beside the command token', () => {
+    render(
+      <NativeChatPickerMenu
+        autocomplete={autocomplete({
+          items: buildNativeChatPickerItems(
+            sessionSlashCommandSuggestions('claude', [
+              {
+                name: 'goal',
+                kind: 'command',
+                description: 'Set a goal and keep working until it is met',
+                argumentHint: '<objective>'
+              },
+              { name: 'clear', kind: 'command' },
+              { name: 'wordy', kind: 'command', argumentHint: `<${'a'.repeat(200)}>` }
+            ]),
+            [],
+            '',
+            '/'
+          )
+        })}
+        activeIndex={0}
+        listboxId="picker"
+        onChoose={vi.fn()}
+        onRetry={vi.fn()}
+      />
+    )
+    const goal = screen.getByRole('option', { name: /goal/i })
+    expect(goal.textContent).toContain('<objective>')
+    expect(goal.textContent).toContain('Set a goal and keep working until it is met')
+    // A command the report left hintless renders its row unchanged.
+    expect(screen.getByRole('option', { name: /clear/i }).textContent).toBe(
+      '/clearClear conversation history'
+    )
+    // A hint long enough to swamp the row is capped before it reaches the DOM.
+    expect(screen.getByRole('option', { name: /wordy/i }).textContent).toBe(
+      `/wordy<${'a'.repeat(79)}`
+    )
+  })
+
   it('announces a successful empty skill result distinctly from loading', () => {
     render(
       <NativeChatPickerMenu

src/renderer/src/components/native-chat/NativeChatAutocompleteMenus.tsx

@@ -209,7 +209,14 @@ function PickerOption({
         <Package className="mt-0.5 size-3.5 shrink-0 text-muted-foreground" />
       ) : null}
       <span className="min-w-0 flex-1">
-        <span className="block truncate font-mono font-medium">{item.token}</span>
+        <span className="flex min-w-0 items-baseline gap-1.5">
+          <span className="min-w-0 truncate font-mono font-medium">{item.token}</span>
+          {item.kind === 'command' && item.argumentHint ? (
+            <span className="min-w-0 truncate font-mono text-[11px] text-muted-foreground">
+              {item.argumentHint}
+            </span>
+          ) : null}
+        </span>
         {item.description ? (
           <span className="block truncate text-xs text-muted-foreground">{item.description}</span>
         ) : null}

src/renderer/src/components/native-chat/native-chat-picker-items.ts

@@ -21,6 +21,8 @@ export type NativeChatPickerItem =
       /** Exactly what a pick inserts — the form the agent invokes. */
       token: string
       description?: string
+      /** How the provider says the command is invoked, e.g. `<objective>`. */
+      argumentHint?: string
       skillCollision: boolean
     }
   | {
@@ -80,6 +82,9 @@ export function buildNativeChatPickerItems(
         name: command.name,
         token: `/${command.name}`,
         description: command.description ? sanitizePickerText(command.description, 240) : undefined,
+        argumentHint: command.argumentHint
+          ? sanitizePickerText(command.argumentHint, 80)
+          : undefined,
         skillCollision: sharedSigil && skillNames.has(command.name)
       },
       stableOrder: index

src/shared/native-chat-slash-commands.test.ts

@@ -104,16 +104,24 @@ describe('a session that reports its own command surface', () => {
     ])
   })
 
-  it('keeps a reported description on a command the curated catalog never claims', () => {
+  it('keeps a reported description and argument hint the curated catalog never claims', () => {
     expect(
       sessionSlashCommandSuggestions('codex', [
         {
           name: 'opsx:apply',
           kind: 'command',
           description: 'Apply the plan',
+          argumentHint: '<plan-id>',
           kindUnspecified: true
         }
       ])
-    ).toEqual([{ name: 'opsx:apply', description: 'Apply the plan', kindUnspecified: true }])
+    ).toEqual([
+      {
+        name: 'opsx:apply',
+        description: 'Apply the plan',
+        argumentHint: '<plan-id>',
+        kindUnspecified: true
+      }
+    ])
   })
 })

src/shared/native-chat-slash-commands.ts

@@ -12,6 +12,8 @@ export type SlashCommandSuggestion = {
   name: string
   /** Optional one-line description for the suggestion row. */
   description?: string
+  /** Provider-authored argument sketch, e.g. `<objective>`. */
+  argumentHint?: string
   kindUnspecified?: true
 }
 
@@ -111,6 +113,7 @@ export function sessionSlashCommandSuggestions(
       return {
         name: entry.name,
         ...(description ? { description } : {}),
+        ...(entry.argumentHint ? { argumentHint: entry.argumentHint } : {}),
         ...(entry.kindUnspecified ? { kindUnspecified: true as const } : {})
       }
     })