fix(detect): keep .tfvars out of the graph under the sensitive-dir carve-out (follow-up to #1955)

The #1943 carve-out rescues genuine source under secrets/ / credentials/, but
.tfvars sits in CODE_EXTENSIONS while being Terraform's canonical values store
(routinely real secrets), so it would now be indexed. Add .tfvars to
_SECRET_PRONE_DATA_EXTS so the shared graphable-source predicate drops it in
both Stage 1 and Stage 3; .tf/.hcl stay graphable as genuine infra source.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

graphify/detect.py

@@ -144,6 +144,10 @@ _GENERIC_KEYWORD_PATTERNS = [
 _SECRET_PRONE_DATA_EXTS = frozenset({
     ".json", ".yaml", ".yml", ".toml", ".ini", ".cfg", ".conf", ".config",
     ".xml", ".properties", ".env", ".txt",
+    # .tfvars is Terraform's canonical VALUES store (routinely holds real
+    # secrets), not source — keep it out of the graph even though it sits in
+    # CODE_EXTENSIONS. .tf/.hcl are genuine infra source and stay graphable.
+    ".tfvars",
 })
 
 # Word separators for the load-bearing check (underscore intentionally included;

tests/test_detect.py

@@ -1108,6 +1108,16 @@ def test_sensitive_dir_carveout_does_not_bypass_name_screens():
     assert _is_sensitive(Path("credentials/id_rsa"))           # extensionless key
 
 
+def test_sensitive_dir_carveout_still_drops_tfvars_values_store():
+    # #1943 follow-up: genuine source under secrets/ is rescued, but .tfvars is
+    # Terraform's canonical values store (real secrets), not source — it stays
+    # dropped, while the real code file beside it is kept.
+    assert _is_sensitive(Path("secrets/prod.tfvars"))
+    assert not _is_sensitive(Path("secrets/loader.py"))
+    # .tf / .hcl are genuine infra source and remain graphable under secrets/.
+    assert not _is_sensitive(Path("secrets/main.tf"))
+
+
 # ── Generic keywords must be load-bearing: topic slugs are not secret stores ──
 # A keyword buried mid-phrase in a >=3-word descriptive name is a note ABOUT
 # the topic, not a credential file. It must not be silently dropped.