TEST-26: a missing value in a check is a named FAIL, not a traceback

Checks and prints that indexed an empty list, exhausted next(), or formatted
None killed the rest of their file (FCST-06). Read them through the new
named_absence.py (nth/first/field/given/present) and conjoin a presence term.

- every site in the brief, plus the family the new scan and a sweep found
- test_named_absence.py: scans every test_*.py for unguarded filtered-list
  indexing, next() without a default and numeric formats on maybe-None
  names; proven to bite; prints what it cannot see, counted
- test_price.py 16a: the `_T17_CAPS is _T17_CAPS` tautology now grades the
  two assemble() calls' arguments
- test_control.py: coverage table re-measured on runs graded to the end

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwRLw7eKYj2byVdwB6kbjU

goodwe_controller/test_static_tariff.py

@@ -63,6 +63,8 @@ import ast
 import gzip
 import json
 import sys
+
+from named_absence import first
 from datetime import datetime, timedelta, timezone
 from pathlib import Path
 
@@ -1213,8 +1215,9 @@ check("...and the pin is not vacuous: each of those names really is a "
 
 def _t17_sig(module, name):
     tree = ast.parse((HERE / "app" / module).read_text(encoding="utf-8"))
-    fn = next(n for n in tree.body
-              if isinstance(n, ast.FunctionDef) and n.name == name)
+    fn = first((n for n in tree.body
+                if isinstance(n, ast.FunctionDef) and n.name == name),
+               f"def {name} in {module}")
     return [a.arg for a in fn.args.args]