Why

This slice improves Slack Block Kit usage for native slash command argument menus by using static_select when choices are too large for a single button row.

Dependency

• Depends on Slack: improve Block Kit interaction handling (foundation) #18180 and feat(slack): capture Block Kit view_closed lifecycle events #18234.
• If reviewing before dependencies merge, review tip commit: 24febd3b2.

What This PR Adds

• In /Users/solvely/Projects/OpenClaw/src/slack/monitor/slash.ts:
  • keeps button menus for small choice sets (<= 5)
  • uses static_select menus for larger sets (> 5), chunked to Slack limits (100 options/select)
  • preserves existing action ID routing (openclaw_cmdarg)
  • supports both interaction payload shapes:
    • button click via action.value
    • select pick via action.selected_option.value

Behavior Changes

• Small arg menus remain button-based.
• Large arg menus render as dropdown selects, reducing block sprawl and improving UX.
• Existing button flows remain backward compatible.

Validation

• pnpm test src/slack/monitor/slash.test.ts
• pnpm check

Reviewer Focus

• src/slack/monitor/slash.ts
• src/slack/monitor/slash.test.ts