docs: update help text and docs for all gateway target types

[aidandaly24]

Description

Update CLI help text and documentation to cover all 5 gateway target types that are now supported:

• mcp-server — external MCP server endpoints
• api-gateway — existing Amazon API Gateway REST APIs
• open-api-schema — auto-derive tools from OpenAPI JSON specs
• smithy-model — auto-derive tools from Smithy JSON models
• lambda-function-arn — connect to existing Lambda functions by ARN

Changes:

• Fix --type help text in GatewayTargetPrimitive.ts to list all 5 types (was missing open-api-schema and smithy-model)
• Update docs/commands.md: add CLI examples for all target types, complete flags table (22 flags) with per-type applicability notes, auth compatibility note
• Update docs/gateway.md: add subsections for each target type with CLI examples, auth support notes, and path resolution details. Update outbound auth table with "Supported Target Types" column including IAM role row.

Related Issue

Type of Change

• Documentation update

Testing

How have you tested the change?

• I ran npm run test:unit and npm run test:integ
• I ran npm run typecheck
• I ran npm run lint
• If I modified src/assets/, I ran npm run test:update-snapshots and committed the updated snapshots

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

[tejaskash]

Requesting changes