feat(gateway): add delete commands

[aidandaly24]

Summary

• add Gateway, Target, connector-backed Target, and Rule delete commands
• keep Gateway deletion non-cascading and delegate dependency enforcement to the service
• implement Connector delete as a Target facade that verifies the selected Target is connector-backed before deletion
• keep Gateway, Target, and Rule Core methods as direct SDK command mappings

IAM scope

• this PR does not mutate execution-role permissions or delete IAM roles
• execution-role ownership and cleanup remain deferred to the shared IAM management plane

Stack

• base: feat(gateway): add update commands #1900
• this PR: feat(gateway): add delete commands #1901

Testing

• focused command registration, selector validation, Connector classification, and Core SDK mapping tests
• fixture-backed Rule, Target, Connector, and Gateway deletion through the real router and Core
• Delete fixtures contain only Connector preflight/Get and Delete SDK exchanges; prerequisites are provisioned directly only while recording
• live recording with AWS_PROFILE=e2e-test verified asynchronous deletion and cleanup of the disposable Gateway and IAM role
• full Gateway suite, build, lint, formatting, and changed-file type checks

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.84%. Comparing base (0e33398) to head (49b388c).

Additional details and impacted files

@@             Coverage Diff              @@
##           refactor    #1901      +/-   ##
============================================
+ Coverage     96.81%   96.84%   +0.02%     
============================================
  Files           329      333       +4     
  Lines         18754    18896     +142     
============================================
+ Hits          18157    18299     +142     
  Misses          597      597              

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[nborges-aws]

No findings from me; super clean PR. Good work!