feat(project): add gateway resources

[aidandaly24]

Summary

Adds project-based Gateway mutation commands:

agentcore project add gateway
agentcore project add gateway-target
agentcore project add gateway-connector

Project-command JSON maps directly to the existing version 1 agentcore.json schemas:

• --authorizer-configuration accepts GatewayAuthorizerConfigSchema;
• --target-configuration accepts one complete AgentCoreGatewayTargetSchema object;
• --connector-configuration accepts the same complete Target object and requires targetType: "connector";
• JSON sources work inline, through file://, and through stdin;
• SDK request shapes are not accepted or translated.

Scalar endpoint, Runtime, and curated connector shortcuts remain. They construct the same
project-schema objects accepted through JSON.

The change also:

• replaces SDK protocol JSON with the direct --enable-semantic-search project field;
• makes project-owned compute Target branches reachable through direct Target JSON;
• validates OAuth/API-key credential-name references in complete Target JSON and OAuth shortcuts;
• validates Runtime and Runtime endpoint references;
• validates the complete candidate project before one agentcore.json write;
• uses the existing generic project-resource mutation flow, with only nested Target placement
  handled specially;
• rejects duplicate Target names across all Gateways and unassignedTargets[], matching the old
  CLI and existing L3 output contract.

No project schema files change. The CLI does not create or copy files referenced by Target JSON;
paths such as schemaSource.inline.path and lambdaFunctionArn.toolSchemaFile remain explicit in
agentcore.json.

Testing

Rebased onto upstream/refactor at 38c30ae4; verification ran on PR head 854514eb.

• bun run format:check
• bun run lint:check
• bun run typecheck
• focused Gateway command tests: 50 passed
• Gateway add handler line coverage: 100%
• bun test src outside the restricted sandbox: 1,789 passed
• bun run build
• built CLI help verified for all three command leaves
• tests are colocated with each Gateway command and share only project-routing setup
• verified complete Target JSON round-trips without translation
• verified direct Target JSON works inline, through file://, and through stdin
• verified project-owned Lambda compute Target JSON is accepted
• verified duplicate Target names are rejected across Gateways and unassignedTargets[]
• verified synthesis uses the existing Target-name-only L3 output contract without CDK changes

Live deployment

Earlier end-to-end verification of the same persisted Gateway shapes used a clean generated project
in account 603141041947, region us-west-2, with
@aws/agentcore-cdk@0.1.0-alpha.45.

• Added an unrestricted Gateway and project Runtime Target through scalar command flags.
• Added an MCP Gateway and external MCP Target through complete direct project JSON.
• Added a Web Search Target through gateway-connector; synthesis produced the expected connector
  configuration and IAM dependency. The service rejected live Target creation because
  Connector integration web-search is not available for this account.
• Alpha.45 emits SearchType: NONE when MCP semantic search is disabled, which current
  CloudFormation rejects. The deployment fixture used project add gateway --protocol mcp --enable-semantic-search, allowing deployment without changing the CLI or L3 dependency.
• Deployed the Runtime, both Gateways, and the Runtime/direct-MCP Targets; all reported READY.
• Invoked runtime-target/invocations through the Gateway and received HTTP 200 with
  runtime gateway works.
• Sent MCP initialize and tools/list through the MCP Gateway; both returned HTTP 200 and the
  direct DeepWiki Target tools were listed.
• Destroyed the stack and independently verified the stack, Runtime, both Gateways, and both
  Targets return not-found.

Credential-provider authoring is owned by the separate project credentials commands. This PR
validates Gateway Target references to those project credentials but does not create them.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.30%. Comparing base (38c30ae) to head (854514e).

Additional details and impacted files

@@             Coverage Diff              @@
##           refactor    #2028      +/-   ##
============================================
+ Coverage     97.24%   97.30%   +0.05%     
============================================
  Files           396      400       +4     
  Lines         24019    24531     +512     
============================================
+ Hits          23357    23869     +512     
  Misses          662      662              

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.