chore: adopt dryvist org-default gitignore

[JacobPEvans-personal]

Summary

Standardizes .gitignore coverage as part of an org-wide hygiene initiative.
Ensures common credential, secret-material, infrastructure-state, and tool-local
artifact paths are ignored consistently across dryvist repos, so files that
shouldn't be in version control aren't tracked by accident.

Adopts the relevant subset of the org-default baseline (dryvist/.github →
configs/gitignore). Append-only and de-duplicated — no existing entries are
modified or removed. Verified that no currently-tracked file becomes ignored.

Intentional carve-outs preserved (committed by convention): .envrc,
*.sops.*, and .terraform.lock.hcl.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request updates the .gitignore file to exclude environment files, private keys, Ansible Vault files, generic secrets, cloud provider credentials, Doppler caches, Terraform states, and AI assistant local states. Feedback suggests refining several patterns: allowing encrypted Ansible Vault files (vault.yml/vault.yaml) to be committed, adding negations to prevent public keys (.pub) from being ignored, narrowing down the overly broad *credentials* pattern to avoid matching source code or documentation, and ensuring setup documentation like SECRETS_SETUP.md is not ignored.