fix(preset): use default enquirer import so interactive workspace creation works

[nx-plugin-for-aws]

Reason for this change

Creating a workspace interactively (without --no-interactive) crashed:

 NX   enquirer.prompt is not a function
    at presetGenerator (.../@aws/nx-plugin/src/preset/generator.js:125:49)

import * as enquirer compiles to a native ESM namespace import since the plugin migrated to ESM (#853). enquirer is a CommonJS package whose prompt is assigned as a runtime static, which cjs-module-lexer can't surface as a named export — so enquirer.prompt was undefined. Under the old CommonJS output the same import * as compiled to require() and worked, so this regressed with the ESM migration.

Description of changes

• Fix the crash: switch to a default import (import enquirer from 'enquirer'), for which enquirer.prompt resolves correctly.
• Prevent a hang: guard the engagementId prompt on process.stdin.isTTY. create-nx-workspace runs the preset via exec, which gives it a data-less stdin pipe (the parent TTY is never forwarded across an exec boundary). Once the crash is fixed, prompting there would hang forever. With the guard, the prompt is skipped when there's no terminal, and creation completes. The prompt still runs when the preset is invoked directly via nx generate in a real terminal (the same spawn/inherited-TTY path the agent-chat CLI uses).
• Test coverage: rename the no-interactive smoke test to create-workspace and add an interactive case that drives the preset generator through a PTY (node-pty, mirroring local-dev.spec.ts's chatStreamsReply) and answers the engagementId prompt — covering the previously untested interactive path. CI/PR matrix entry renamed accordingly.

Description of how you validated changes

• Verified the module shape: with import * as enquirer, enquirer.prompt is undefined; with the default import it's a function.
• Ran the create-workspace smoke test locally against the fixed build: the non-interactive npm/pnpm/yarn-4 cases pass, and the new interactive case drives the engagementId prompt end-to-end (types MyEngagementId, submits, asserts it's written as a tag in aws-nx-plugin.config.mts). (bun and yarn-classic fail only due to local env — bun not installed, and a local verdaccio transitive-dep passthrough quirk.)
• pnpm nx run @aws/nx-plugin:build passes (lint + unit tests, 33 preset tests green).

Issue # (if applicable)

Closes #897.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.36%. Comparing base (6edf130) to head (7a59ea8).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

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  Coverage   87.36%   87.36%           
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  Files         155      155           
  Lines        5388     5388           
  Branches     1263     1263           
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  Hits         4707     4707           
  Misses        359      359           
  Partials      322      322           

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