feat(cli): select an AWS profile for installer commands

[be-student]

Description

Add --profile NAME to the AWS installer, destroy command, and standalone demo launcher. --profile NAME alone opens the interactive CLI; combining it with deployment flags retains the existing non-interactive flow.

The command selects AWS_PROFILE before creating SDK clients or signing credential providers, so credential checks, resource operations, and SigV4 requests use the same SDK profile selection. An explicit flag overrides the inherited profile; omitting it preserves the existing SDK credential chain. Blank profile names are rejected. Region behavior and AWS configuration files are unchanged.

Public deployment docs describe usage and precedence. The contributor README records the initialization boundary. The existing docs page title and description are unchanged, so the generated llms.txt index does not require regeneration.

Issues Resolved

Closes #395.

Validation

• Reproduced before implementation: the real installer rejected --profile as an unknown option.
• npm test in aws/cli-installer: 139 passed on Node 26.
• The same unit and e2e-unit files on CI's Node 24: 139 passed.
• Tests cover profile-only interactive routing, create/destroy parsing, the real dry-run entrypoint, blank profile rejection in all entrypoints, and real SDK service/signing credential providers using isolated temporary credential files. Profile tests make no AWS API calls.
• npm run build in docs: passed, including the nested Starlight build and link validation (148 documentation pages).
• git diff --check: passed.

Implemented and reviewed by Codex. No live AWS deployment was performed; cloud provisioning and SSO login are not claimed as validated.

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