feat(tui): replace /clear double-press gate with a proper confirm overlay

The time-window gate felt wrong — users would hit /clear, read the
prompt, retype, and consistently blow past the window. Swapping to a
real yes/no overlay that blocks input like the existing Approval and
Clarify prompts.

- add ConfirmReq type + OverlayState.confirm + $isBlocked coverage
- ConfirmPrompt component (prompts.tsx): cancel row on top as the
  default, danger-coloured confirm row on the bottom, Y/N hotkeys,
  Enter on default = cancel, Esc/Ctrl+C cancel
- wire into PromptZone (appOverlays.tsx)
- /clear + /new now push onto the overlay instead of arming a timer
- HERMES_TUI_NO_CONFIRM=1 still skips the prompt for scripting
- drop the destructiveGate + createSlashHandler reset wiring
  (destructive.ts and its tests removed)

Refs #4069.

ui-tui/src/app/createSlashHandler.ts

@@ -3,7 +3,6 @@ import type { SlashExecResponse } from '../gatewayTypes.js'
 import { asCommandDispatch, rpcErrorMessage } from '../lib/rpc.js'
 
 import type { SlashHandlerContext } from './interfaces.js'
-import { destructiveGate, isDestructiveCommand } from './slash/commands/core.js'
 import { findSlashCommand } from './slash/registry.js'
 import type { SlashRunCtx } from './slash/types.js'
 import { getUiState } from './uiStore.js'
@@ -41,17 +40,11 @@ export function createSlashHandler(ctx: SlashHandlerContext): (cmd: string) => b
     const found = findSlashCommand(parsed.name)
 
     if (found) {
-      if (!isDestructiveCommand(found.name)) {
-        destructiveGate.reset()
-      }
-
       found.run(parsed.arg, runCtx, cmd)
 
       return true
     }
 
-    destructiveGate.reset()
-
     if (catalog?.canon) {
       const needle = `/${parsed.name}`.toLowerCase()
 

ui-tui/src/app/interfaces.ts

@@ -10,6 +10,7 @@ import type {
   ActivityItem,
   ApprovalReq,
   ClarifyReq,
+  ConfirmReq,
   DetailsMode,
   Msg,
   PanelSection,
@@ -53,6 +54,7 @@ export interface GatewayProviderProps {
 export interface OverlayState {
   approval: ApprovalReq | null
   clarify: ClarifyReq | null
+  confirm: ConfirmReq | null
   modelPicker: boolean
   pager: null | PagerState
   picker: boolean

ui-tui/src/app/overlayStore.ts

@@ -5,6 +5,7 @@ import type { OverlayState } from './interfaces.js'
 const buildOverlayState = (): OverlayState => ({
   approval: null,
   clarify: null,
+  confirm: null,
   modelPicker: false,
   pager: null,
   picker: false,
@@ -17,8 +18,8 @@ export const $overlayState = atom<OverlayState>(buildOverlayState())
 
 export const $isBlocked = computed(
   $overlayState,
-  ({ approval, clarify, modelPicker, pager, picker, secret, skillsHub, sudo }) =>
-    Boolean(approval || clarify || modelPicker || pager || picker || secret || skillsHub || sudo)
+  ({ approval, clarify, confirm, modelPicker, pager, picker, secret, skillsHub, sudo }) =>
+    Boolean(approval || clarify || confirm || modelPicker || pager || picker || secret || skillsHub || sudo)
 )
 
 export const getOverlayState = () => $overlayState.get()

ui-tui/src/app/slash/commands/core.ts

@@ -1,7 +1,6 @@
 import { NO_CONFIRM_DESTRUCTIVE } from '../../../config/env.js'
 import { dailyFortune, randomFortune } from '../../../content/fortunes.js'
 import { HOTKEYS } from '../../../content/hotkeys.js'
-import { createDestructiveGate } from '../../../domain/destructive.js'
 import { nextDetailsMode, parseDetailsMode } from '../../../domain/details.js'
 import type {
   ConfigGetValueResponse,
@@ -15,12 +14,6 @@ import { patchOverlayState } from '../../overlayStore.js'
 import { patchUiState } from '../../uiStore.js'
 import type { SlashCommand } from '../types.js'
 
-export const destructiveGate = createDestructiveGate()
-
-const DESTRUCTIVE_COMMANDS = new Set(['clear', 'new'])
-
-export const isDestructiveCommand = (name: string) => DESTRUCTIVE_COMMANDS.has(name)
-
 const flagFromArg = (arg: string, current: boolean): boolean | null => {
   if (!arg) {
     return !current
@@ -90,14 +83,27 @@ export const coreCommands: SlashCommand[] = [
         return
       }
 
-      const label = cmd.startsWith('/new') ? '/new' : '/clear'
+      const isNew = cmd.startsWith('/new')
 
-      if (!NO_CONFIRM_DESTRUCTIVE && !destructiveGate.request('clear')) {
-        return ctx.transcript.sys(`press ${label} again to confirm — starts a new session`)
+      const commit = () => {
+        patchUiState({ status: 'forging session…' })
+        ctx.session.newSession(isNew ? 'new session started' : undefined)
       }
 
-      patchUiState({ status: 'forging session…' })
-      ctx.session.newSession(cmd.startsWith('/new') ? 'new session started' : undefined)
+      if (NO_CONFIRM_DESTRUCTIVE) {
+        return commit()
+      }
+
+      patchOverlayState({
+        confirm: {
+          cancelLabel: 'No, keep going',
+          confirmLabel: isNew ? 'Yes, start a new session' : 'Yes, clear the session',
+          danger: true,
+          detail: 'This ends the current conversation and clears the transcript.',
+          onConfirm: commit,
+          title: isNew ? 'Start a new session?' : 'Clear the current session?'
+        }
+      })
     }
   },