new-backendlisted

# Add a new observability backend to otel-as-code The machine-readable vendor list has a single source (`backends.txt`). Adding a backend is: register it there, add its per-vendor content, then a validated snapshot. Ask for the vendor name and its Terraform provider source if not given. ## 1. Register the vendor (single source of truth) Add the vendor name (one per line) to `backends.txt` at the repo root. This is the ONLY place the list is enumerated — the CI `validate-terraform` loop, `tests/check-snapshots.sh`, the `session-summary` hook, and `/otel-backend`'s validation all read it. ## 2. terraform-patterns skill Add a `## <Vendor>` section to `skills/terraform-patterns/SKILL.md`: provider `source` + version, auth variables, required resources (dashboard / alerts / SLO), key gotchas, and OTel-specific query examples (PromQL/NRQL/native). ## 3. terraform-gen subagent Add a `## <Vendor> main.tf` block to `agents/terraform-gen.md` describing the resources to emit, referencing the skill section. ## 4. Golden snapshot (validated) Create `tests/snapshots/<vendor>/main.tf.snap`: - Make it SELF-CONTAINED — declare its own `variable` blocks with defaults — so CI can `terraform validate` `main.tf` standalone (the job copies only `main.tf.snap`). - For an unfamiliar provider, introspect the real schema instead of guessing: after `terraform init`, run `terraform providers schema -json` to get exact resource names and required fields. - Validate: copy to a temp dir, `terraform in