Rename build_all_dags to build_all_airflow_dags for safe-mode discovery

[jeremybeard]

What

Renames the DAG-loading entry point from build_all_dags to build_all_airflow_dags so that a minimal one-line loader is actually discovered by Airflow. build_all_dags and build_all remain as deprecated aliases that emit DeprecationWarning and forward.

Why

Airflow's DAG file processor runs in safe mode by default. Its discovery heuristic (airflow.utils.file.might_contain_dag) only treats a file as a potential DAG file when its contents contain both the airflow and dag substrings:

content = content.lower()
if b"airflow" not in content:
    return False
return any(s in content for s in (b"dag", b"asset"))

The previous entry point build_all_dags carries dag but not airflow. So the canonical loader we ship and document:

from blueprint import build_all_dags
build_all_dags()

contains no airflow substring and is silently skipped by Airflow — no error, just missing DAGs. It only worked when something unrelated (e.g. from airflow import DAG for a type hint) happened to drag the airflow substring into the file. That is exactly the trap users hit.

build_all_airflow_dags puts both required substrings in the import line itself, so the bare-minimum loader works with nothing else in the file:

from blueprint import build_all_airflow_dags
build_all_airflow_dags()

Independent integration test for the bare-minimum loader

tests/integration/test_safe_mode_discovery.py is new and self-contained. It writes the bare-minimum loader (import + call, nothing else — no from airflow import DAG, no docstring) and asserts Airflow's real safe-mode scanner picks it up:

• test_bare_minimum_loader_is_discovered_by_safe_mode — the new build_all_airflow_dags loader passes might_contain_dag(..., safe_mode=True).
• test_legacy_loader_is_skipped_by_safe_mode — the pre-rename build_all_dags loader is skipped, documenting the regression this fixes.

It calls Airflow's actual discovery function rather than a re-implementation, so it cannot drift from real behaviour, and it needs no running Airflow instance (no Astro standalone), so it runs fast and in isolation from the API-driven integration tests.

Changes

• blueprint/builder.py: real function renamed to build_all_airflow_dags; build_all_dags + build_all are deprecating aliases.
• blueprint/__init__.py: export build_all_airflow_dags (aliases still exported).
• blueprint/cli.py: blueprint new scaffold output uses the new name.
• examples/, README.md: loaders and docs use build_all_airflow_dags. The simple example is the bare-minimum loader.
• tests/test_builder.py: functional tests target the real function; added a deprecation test for build_all_dags.
• tests/integration/project/dags/loader.py: uses the new name.

Verification

• 266 unit tests pass; ruff and ty clean.
• New safe-mode tests pass (2/2), including the negative case proving the old name was skipped.

Notes

• This is the second rename of this symbol (build_all → build_all_dags → build_all_airflow_dags). The first rename only added the dag substring and never fixed discovery, because its premise — that Airflow needs either dag or airflow — was wrong; it needs both. Both old names are kept as forwarding aliases, so existing loaders keep working with a deprecation warning.