Add support for deleting ondemand requests by request-id

This change enables floaty delete to accept request-ids (UUID format)
in addition to hostnames. When a request-id is detected, floaty will:

1. Cancel pending ondemand requests by marking status as 'deleted'
2. Move any already-provisioned VMs to the termination queue

Implementation:
- Modified Pooler.delete to detect UUID format and use ondemandvm endpoint
- Updated command syntax and examples to document request-id support
- Added comprehensive tests for request-id deletion
- Fixed Ruby 3.1+ compatibility by adding abbrev and base64 gems

Fixes issue where users had no way to cancel ondemand requests or
bulk-delete VMs from a completed request.

Gemfile.lock

@@ -8,9 +8,11 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
+    abbrev (0.1.2)
     addressable (2.8.6)
       public_suffix (>= 2.0.2, < 6.0)
     ast (2.4.2)
+    base64 (0.3.0)
     bigdecimal (3.1.8)
     coderay (1.1.3)
     commander (4.6.0)
@@ -107,9 +109,12 @@ GEM
 
 PLATFORMS
   aarch64-linux
+  arm64-darwin-25
   x86_64-linux
 
 DEPENDENCIES
+  abbrev
+  base64
   pry
   rake
   rb-readline