feat(cli): wire Cursor /summarize and /clear slash builtins (#747)

* feat(cursor): wire /summarize and /clear slash builtins for remote sessions

Seed cursor builtins for web autocomplete, parse summarize/clear in
cursorRemoteLauncher (pass-through to agent -p; reject /clear with args).

Fixes tiann/hapi#738

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(cursor): isolate slash commands before message queue batching

Parse summarize/clear at enqueue time (runCursor) with pushIsolateAndClear
so waitForMessagesAndGetAsString never merges a slash with the next prompt.
Adds queue policy tests for invalid /clear + following message.

Addresses PR #747 review.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(cursor): preserve pending messages when isolating slash commands

pushIsolateAndClear() wipes the entire queue, so a normal prompt queued
before /summarize or /clear would be silently dropped. Add pushIsolated()
- isolation without clearing - and route Cursor slash commands through
it instead. Adds queue tests covering the preserve-then-isolate path.

Addresses PR #747 review.

Co-authored-by: Cursor <cursoragent@cursor.com>

---------

Co-authored-by: Cursor <cursoragent@cursor.com>

shared/src/slashCommands.ts

@@ -39,7 +39,10 @@ export const BUILTIN_SLASH_COMMANDS = {
         { name: 'default', description: 'Return OpenCode permission mode to default', source: 'builtin' },
         { name: 'init', description: 'Generate or refresh AGENTS.md for this project', source: 'builtin' },
     ],
-    cursor: [],
+    cursor: [
+        { name: 'summarize', description: 'Summarize conversation context to free window space (pass-through to Cursor agent)', source: 'builtin' },
+        { name: 'clear', description: 'Clear conversation context if supported by Cursor agent', source: 'builtin' },
+    ],
 } as const satisfies Record<string, readonly SlashCommand[]>
 
 export function getBuiltinSlashCommands(agent: string): SlashCommand[] {