fix: Generated compose emits FORGE_BOT_USER_LLAMA — legacy name, should derive from forge_user (#849)

Key `FORGE_BOT_USER_*` on `$user_upper` (forge_user normalized with
`tr 'a-z-' 'A-Z_'`) instead of `${service_name^^}`, matching the
`FORGE_TOKEN_<FORGE_USER>` / `FORGE_PASS_<FORGE_USER>` convention two
lines above in the same emitted block. For `[agents.llama]` with
`forge_user = "dev-qwen"` this emits `FORGE_BOT_USER_DEV_QWEN: "dev-qwen"`
instead of the legacy `FORGE_BOT_USER_LLAMA`.

No external consumers read `FORGE_BOT_USER_*` today (verified via grep),
so no fallback/deprecation shim is needed — this is purely a one-site
fix at the sole producer.

Adds `tests/lib-generators.bats` as a regression guard. Follows the
existing `tests/lib-*.bats` pattern (developer-run, not CI-wired).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/generators.sh

@@ -149,7 +149,7 @@ _generate_local_model_services() {
       PROJECT_REPO_ROOT: /home/agent/repos/${PROJECT_NAME:-project}
       WOODPECKER_DATA_DIR: /woodpecker-data
       WOODPECKER_REPO_ID: "${wp_repo_id}"
-      FORGE_BOT_USER_${service_name^^}: "${forge_user}"
+      FORGE_BOT_USER_${user_upper}: "${forge_user}"
       POLL_INTERVAL: "${poll_interval_val}"
       GARDENER_INTERVAL: "${GARDENER_INTERVAL:-21600}"
       ARCHITECT_INTERVAL: "${ARCHITECT_INTERVAL:-21600}"