docs(runner): name the protoc coupling and fix a mechanism claim

Both from the cross-review, both fair.

"Go setzt CGO_ENABLED=0" is right about the effect and wrong about the
mechanism: Go does not set the variable, cgo simply stays off when no C
compiler is found, and go env then reports 0. Reworded.

And protoc on an instance-wide runner ties every repository to the
distribution's version -- 3.21.x on Debian 12. Unlike make and gcc that is a
code generator, so a distro upgrade changes generated code for all users at
once. The comment says so now, and says where a project that needs its own
version should pin it instead of raising it here for everybody.

README.md

@@ -13,7 +13,7 @@ Inspired by [community-scripts/ProxmoxVE](https://github.com/community-scripts/P
 | [nexus](ct/nexus.sh) | App LXC for [nexus](https://gitea.luki-net.org/l.kirchner/nexus-hub) (Family Knowledge Hub): host-mode runner (label `nexus`, CI + deploy), service skeleton, `/opt/nexus` layout. Runtime is provisioned/extended via [`install/nexus-runtime.sh`](install/nexus-runtime.sh) (idempotent, re-runnable) | ✅ in production |
 | [nexus-db](ct/nexus-db.sh) | PostgreSQL 16 + pgvector for nexus — least-privilege role, pg_hba allowlist (only the nexus LXC), DSN handed over via credentials file | ✅ in production |
 | [authentik](ct/authentik.sh) | Central homelab IdP (official Docker Compose via LXC nesting) — headless bootstrap admin **and** API token for agent-driven blueprint configuration, blueprints mount, permanent auth domain (WebAuthn RP-ID) | ✅ in production |
-| [runner](ct/runner.sh) | General **instance-wide** Gitea Actions runner (label `homelab`) — Docker for throwaway CI test containers, deliberately **no** sudoers/deploy rights | 🔄 in review ([PR #6](https://gitea.luki-net.org/luki-net/proxmox-scripts/pulls/6)) |
+| [runner](ct/runner.sh) | General **instance-wide** Gitea Actions runner (label `homelab`) — Docker for throwaway CI test containers, deliberately **no** sudoers/deploy rights | ✅ in production |
 
 Run any one-liner on a Proxmox VE host as root:
 
@@ -32,12 +32,14 @@ CTID=200 HOSTNAME=devpi DISK_SIZE=30 RAM=4096 CORES=4 IPCFG=dhcp \
 
 All defaults (`DEFAULT_HOSTNAME`, `DEFAULT_DISK`, …) and app config values are settable per call via env vars.
 
+Every input is validated (digits-only for CTID/disk/cores/RAM/VLAN, IP/CIDR/gateway format, hostname/storage charsets). Invalid interactive input re-prompts — including pasted values with invisible control/non-ASCII bytes, which are rejected rather than silently stripped. Env-provided values are validated too and abort the run when malformed (no re-prompt loop in non-interactive use).
+
 ## The pattern
 
 Two files per app, both sourcing the shared libs via `curl`:
 
-- **`ct/<app>.sh`** runs on the PVE host: prompts → unprivileged LXC → pushes a config env file into the container → bootstraps the installer. Apps that need Docker (authentik, runner) enable `nesting+keyctl` automatically.
-- **`install/<app>-install.sh`** runs inside the LXC: packages, unprivileged app user, secrets generated on-host (never printed), systemd units, a `/root/<app>.credentials` notes file — then shreds the bootstrap env. Idempotent where it matters: re-runs skip what exists.
+- **`ct/<app>.sh`** runs on the PVE host: prompts → unprivileged LXC → pushes a config env file into the container → bootstraps the installer. Apps that need Docker (authentik, runner) enable `nesting+keyctl` automatically. The standard prompts include an **SSH root login choice** (`SSH_ROOT_LOGIN`, default yes for homelab convenience; `no` keeps the Debian key-only default) — applied inside the container as an sshd drop-in by `configure_ssh_root_login`.
+- **`install/<app>-install.sh`** runs inside the LXC: packages, unprivileged app user, secrets generated on-host (never printed), systemd units, a `/root/<app>.credentials` notes file — then shreds the bootstrap env. Idempotent where it matters: re-runs skip what exists. `setup_base_apt` also fixes the bare-template **locale situation**: `C.UTF-8` is exported up front (glibc built-in, covers the first apt run without perl warnings), then `en_US.UTF-8` is generated and set as the system default.
 
 Shared libs: [`lib/build.func`](lib/build.func) (host-side: prompts, LXC create, bootstrap) and [`lib/install.func`](lib/install.func) (in-container: apt, users, systemd, http-wait).
 
@@ -50,15 +52,11 @@ Shared libs: [`lib/build.func`](lib/build.func) (host-side: prompts, LXC create,
 
 ## Contributing
 
-**All changes go through a pull request with cross-review** (Claude Code ↔ Codex, or a human) — no direct pushes to `main`. This rule exists because of two real incidents where an un-reviewed script shipped a missing `source build.func` (see wiki → Lessons). CI (`bash -n`, source-check, validation suite) is being introduced with [PR #5](https://gitea.luki-net.org/luki-net/proxmox-scripts/pulls/5) and runs on the `homelab` runner.
+**All changes go through a pull request with cross-review** (Claude Code ↔ Codex, or a human) — no direct pushes to `main`. This rule exists because of two real incidents: a pasted VLAN tag carrying an invisible non-UTF-8 byte broke `pct create` mid-run, and the "missing `source build.func`" bug shipped twice — caught in review on the nexus-db PR, but reaching production via an un-reviewed authentik commit (see wiki → Lessons).
 
-How to add a script: [docs/adding-a-script.md](docs/adding-a-script.md).
+CI (`.gitea/workflows/ci.yml`, instance-wide `homelab` runner from [ct/runner.sh](ct/runner.sh)) enforces on every PR: `bash -n` over all scripts, the "every `ct/*.sh` sources `build.func`" check ([tests/check_ct_source.sh](tests/check_ct_source.sh)) and the validation unit tests ([tests/test_validation.sh](tests/test_validation.sh)); shellcheck runs when available on the runner.
 
-## Contributing (verbindlich seit K-114)
-
-**Alle Änderungen laufen als PR mit Cross-Review** — keine Direkt-Commits auf `main`. Hintergrund: Der „`build.func` nicht gesourct"-Bug hat es einmal bis in die Produktion geschafft (authentik-Anlage), während dieselbe Fehlerklasse im nexus-db-PR vom Review gefangen wurde. Die CI (`.gitea/workflows/ci.yml`, Runner-Label `homelab` — instanzweiter Runner aus `ct/runner.sh`) erzwingt zusätzlich: `bash -n` über alle Scripts, „jedes `ct/*.sh` sourct `build.func`" (`tests/check_ct_source.sh`) und die Validierungs-Unit-Tests (`tests/test_validation.sh`).
-
-Eingaben in `prompt_lxc_config` sind validiert (Ziffern-Checks, IP/CIDR/Gateway-Format, Re-Prompt bei unsichtbaren Steuer-/Non-ASCII-Zeichen — Lesson vom 2026-06-11). Neue App-Prompts bitte über `prompt_validated`/`require_valid` aus `lib/build.func` bauen statt nacktem `read`.
+Build new app prompts on `prompt_validated`/`require_valid` from `lib/build.func` instead of bare `read`. How to add a script: [docs/adding-a-script.md](docs/adding-a-script.md).
 
 ## Repo layout
 
@@ -69,6 +67,9 @@ Eingaben in `prompt_lxc_config` sind validiert (Ziffern-Checks, IP/CIDR/Gateway-
 ├── lib/
 │   ├── build.func      # Shared host-side helpers (prompts, LXC create, bootstrap)
 │   └── install.func    # Shared in-container helpers (apt, systemd, users, http-wait)
+├── tests/
+│   ├── test_validation.sh   # Unit tests for the input validation helpers
+│   └── check_ct_source.sh   # Every ct/*.sh must source build.func
 ├── docs/
 │   └── adding-a-script.md
 ├── README.md

install/runner-install.sh

@@ -63,8 +63,34 @@ valid_token_word "$RUNNER_LABELS" || { msg_err "RUNNER_LABELS enthält unzuläss
 # der unprivilegierte User darf dort nicht schreiben.
 run_user() { runuser -u "$APP_USER" -- env -C "$RUNNER_DIR" HOME="$APP_HOME" "$@"; }
 
-# ── Pakete: git/rsync, Node (checkout-Action), Docker (Test-Container) ────────
-setup_base_apt git rsync ca-certificates curl
+# ── Pakete: git/rsync, Node (checkout-Action), Docker (Test-Container),
+#    Build-Werkzeuge (Compiler-Sprachen in CI) ─────────────────────────────────
+#
+# make/gcc/protobuf: Der Runner faehrt Host-Mode, also gibt es kein Image, das
+# Werkzeuge mitbringt — was hier nicht liegt, hat kein Job. Konkret gemessen an
+# l.kirchner/patchmgr (Go):
+#   make                 "make: command not found" in jedem Gate-Job
+#   gcc                  ohne gefundenen C-Compiler bleibt cgo aus (go env
+#                        meldet dann CGO_ENABLED=0), und "go test -race" ist
+#                        nicht baubar
+#   protobuf-compiler    protoc fuer die Codegenerierung
+#   libprotobuf-dev      liefert /usr/include/google/protobuf/*.proto; ohne die
+#                        Includes scheitert protoc trotz vorhandenem Binary
+#
+# ACHTUNG protoc: Das bindet jedes Repo der Instanz an die protoc-Fassung der
+# Distribution (Debian 12: 3.21.x). Anders als make/gcc ist protoc ein
+# Codegenerator — ein Distro-Upgrade aendert erzeugten Code fuer alle Nutzer
+# gleichzeitig. Wer eine eigene Fassung braucht, pinnt sie im Projekt
+# (Release-Tarball, buf, oder Docker — der Runner hat Docker) statt sie hier
+# zu heben.
+#
+# Bewusst NICHT installiert: sudo. Ein Workflow soll auf diesem Runner nichts
+# nachinstallieren koennen — was gebraucht wird, steht hier.
+#
+# Go selbst gehoert nicht hierher: Projekte holen es ueber actions/setup-go,
+# weil CI-Matrizen mehrere Fassungen fahren.
+setup_base_apt git rsync ca-certificates curl \
+  make gcc protobuf-compiler libprotobuf-dev
 
 NODE_HAVE="$(command -v node >/dev/null 2>&1 && node -v | sed -E 's/^v([0-9]+).*/\1/' || echo 0)"
 if [[ "$NODE_HAVE" != "$NODE_MAJOR" ]]; then