Use destructive hints on JSON specs to provide confirmation DX

[JoshMock]

Adding hints to APIs that are potentially destructive was handled in elastic/schemas-js#25. The hints will be used by MCP and Agent Builder, so we should add a corresponding feature to the CLI.

Proposed experience:

• By default, destructive actions wait for interactive confirmation: This is a potentially destructive action. Do you want to continue? [y/N]
• Confirmation step is skipped if any of the following are true:
  • --yes CLI flag is used
  • YES=true env var is set
  • require_confirmation: false is set in the config file
• allow/blocklist filtering configuration (commands.allowed, commands.blocked) is extended to include commands.block_destructive that takes a boolean.
  • if true, destructive commands are implicitly added to commands.blocked
  • if false or unset, destructive commands are allowed
  • if false but a commands.allowed list is also present, the option is ignored to avoid accidentally making the allowlist overly permissive

[JoshMock]

NOTE: this is not ready to be implemented yet. Finalizing the proposed experience is pending.

[JoshMock]

Related, but smaller scope: #537

[margaretjgu]

done in #537:

• --yes flag and confirmation guard
• interactive prompt on tty when a command is marked destructive
• fails closed with confirmation_required when non interactive and no --yes
• --dry-run skips the prompt since nothing is sent
• cloud delete and other destructive endpoints get explicit intent
• extension remove marked destructive
• cloud reads destructive from @elastic/schemas instead of guessing from the http method

not done:

• yes=true env var
• require_confirmation: false in the config file
• commands.block_destructive
• es and kb still infer destructive from the http method, their definitions come from the generator and don't carry the schema's destructive flag yet