refactor(meshstack/noop): take the runner's GCP project from test_context

.agents/skills/e2e-test/SKILL.md

@@ -91,7 +91,8 @@ Conventions that keep this clean and correct:
 - **Always-shared fields are required**: `workspace`, `name_suffix`, and `hub_git_ref` are used (or
   statically evaluated) in both modes.
 - **Cloud resource IDs live under `fixtures`** (e.g. `var.test_context.fixtures.stackit.project_id`),
-  never as a flat top-level field.
+  never as a flat top-level field. This ensures we have one common union type of fixture inputs reusable
+  across our hub modules.
 - **`test_context` describes the environment, not the test case.** A flag that selects *which variant
   of the module under test to build* (e.g. a sync vs async implementation) does not belong in
   `test_context` — it belongs in a **root variable of the `e2e/` module**, pinned per test file. See
@@ -101,13 +102,13 @@ Conventions that keep this clean and correct:
 
 ### Secrets
 
-**No secret is ever a `test_context` field.** The grab-bag is built from state a CI job can read, so
-a secret in it would have to be persisted somewhere it does not belong.
+**No secret go into the `test_context` field.** The test_context object is built from a tofu state
+read and this must not store secrets.
 
 A secret reaches the module one of two ways:
 
-- The provider reads it from **its own standard environment variable** (cloud credentials). The
-  module declares nothing.
+- The provider reads it from **its own standard environment variable**. The
+  module declares nothing and we rely on the e2e test harness to setup the environment accordingly.
 - The module declares a **flat root variable** for it, when the value is also needed as an input to
   the module under test (e.g. `stackit_git_forgejo_token`, `github_app_private_key`). The smoke-test
   runner exports every secret it holds as `TF_VAR_<name>`, so declaring the variable is all it takes
@@ -489,6 +490,7 @@ source setup-override-provider.sh
 - [ ] `fixtures` is `optional()` with its inner shape fully required (no half-populated fixtures)
 - [ ] Always-shared fields (`workspace`, `name_suffix`, `hub_git_ref`) are required, not `optional()`
 - [ ] Cloud resource IDs sourced from `var.test_context.fixtures.*` (not flat `test_context` fields)
+- [ ] No fixture read from the environment — only secrets arrive as `TF_VAR_*`
 - [ ] Scalar secrets are top-level `nullable` vars with `default = null` (foundation mode omits them)
 - [ ] Module sourced via relative path (not a GitHub URL), gated with `count = var.test_context.bbd_version_ref == null ? 1 : 0`
 - [ ] `hub.git_ref = var.test_context.hub_git_ref` — no hardcoded `"main"`

AGENTS.md

@@ -472,6 +472,10 @@ the diagram checklist.
 
 Modules that can be smoke-tested against a live meshStack instance should include an `e2e/` directory alongside the module root.
 
+An `e2e/` module takes every environment fact from `var.test_context`; only secrets arrive as
+scalar `TF_VAR_*`. A `TF_VAR_*` fixture has to be wired in the harness repo as well, which is a
+second place for it to go missing.
+
 See [.agents/skills/e2e-test/SKILL.md](.agents/skills/e2e-test/SKILL.md) (the `e2e-test` skill) for the full e2e testing conventions, including the `e2e/` structure, `test_context` wiring, `e2e/main.tf` and `*.tftest.hcl` conventions, the new-test checklist, and how to run and debug tests via the smoke-test runner.
 
 <!-- scorecard-checks: no_buildingblock_tftest -->

modules/meshstack/noop/e2e/runner/main.tf

@@ -3,7 +3,7 @@ module "backplane" {
 
   meshstack_workspace_identifier = var.test_context.workspace
   meshstack_endpoint             = var.meshstack_endpoint
-  gcp_project_id                 = var.gcp_project_id
+  gcp_project_id                 = var.test_context.fixtures.gcp.project_id
   gcp_region                     = var.gcp_region
   gcp_resource_name_prefix       = "noop-runner-${var.test_context.name_suffix}"
   runner_display_name            = "smoke-test-noop-runner-${var.test_context.name_suffix}"

modules/meshstack/noop/e2e/runner/provider.tf

@@ -1,4 +1,4 @@
 provider "google" {
-  project = var.gcp_project_id
+  project = var.test_context.fixtures.gcp.project_id
   region  = var.gcp_region
 }

modules/meshstack/noop/e2e/runner/variables.tf

@@ -4,21 +4,25 @@ variable "test_context" {
     workspace   = string
     project     = string
     name_suffix = string
+
+    # Project the runner's Cloud Run service and Secret Manager secrets live in.
+    fixtures = object({
+      gcp = object({
+        project_id = string
+      })
+    })
   })
   nullable = false
 }
 
-variable "gcp_project_id" {
-  type        = string
-  description = "GCP project ID for the runner Cloud Run service and Secret Manager secrets."
-}
-
 variable "gcp_region" {
   type        = string
   default     = "europe-west1"
   description = "GCP region for the Cloud Run service and Secret Manager replicas."
 }
 
+# Not secret, so this belongs in test_context (see the e2e-test skill) — but the harness does not
+# publish it there yet; it reaches CI through the secret pipe. Move it over once it does.
 variable "meshstack_endpoint" {
   type        = string
   description = "Base URL of the meshStack API. Written into the runner config for API polling."