feat(gateway): add update commands

[aidandaly24]

Summary

• add Gateway, Target, connector-backed Target, and Rule update commands
• support explicit set, clear, and no-op validation semantics
• GET current Gateway and Target state, merge requested changes, and send the complete replacement requests required by the service
• keep Rule updates patch-shaped
• preserve complete API access through JSON sources plus focused MCP endpoint and Connector shortcuts
• keep Connector shortcut construction handler-owned and Connector classification local to each layer

IAM scope

• this PR does not create, mutate, or reconcile IAM roles or permission policies
• --role-arn updates only the Gateway service configuration
• execution-role permissions remain customer-managed until the shared IAM management plane lands

Stack

• base: feat(gateway): add create commands #1899
• this PR: feat(gateway): add update commands #1900
• top: feat(gateway): add delete commands #1901

Testing

• focused Gateway validation, flag mapping, request merge, connector classification, and fixture replay tests
• fixture-backed Gateway, Target, Connector, and Rule updates through the real router and Core
• full build, lint, formatting, typecheck, cross-platform unit-test, compiled-binary smoke-test, and AgentCore E2E CI coverage

[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.39640% with 24 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.80%. Comparing base (e932251) to head (f6e7737).

Files with missing lines	Patch %	Lines
src/handlers/gateway/connector/update/index.tsx	89.26%	16 Missing ⚠️
src/handlers/gateway/rule/update/index.tsx	93.15%	5 Missing ⚠️
src/handlers/gateway/target/update/index.tsx	98.24%	2 Missing ⚠️
src/handlers/gateway/update/index.tsx	99.38%	1 Missing ⚠️

Additional details and impacted files

@@                     Coverage Diff                     @@
##           feat/gateway-create-cud    #1900      +/-   ##
===========================================================
+ Coverage                    95.77%   95.80%   +0.02%     
===========================================================
  Files                          296      300       +4     
  Lines                        16748    17414     +666     
===========================================================
+ Hits                         16041    16683     +642     
- Misses                         707      731      +24     

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[aidandaly24]

This function is also here, but I didn't want to import from the handlers into the core. This avoids circular dependencies.

agentcore-cli/src/handlers/gateway/connector/gatewayConnectorTarget.ts

Lines 6 to 11 in c44a4e5

	static is(configuration: TargetConfiguration | undefined): boolean {
	return (
	configuration?.mcp?.connector !== undefined ||
	configuration?.inference?.connector !== undefined
	);
	}