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_packshare.py

@@ -36,6 +36,7 @@ from math import inf
 from pathlib import Path
 
 from app import arbitrage, packshare
+from named_absence import first, nth, present
 from app.allocator import plan
 from app.arbiter import (
     ACTUATOR_SITE, CLAIM_SCOPE, P_LOOP, P_SAFETY, SCOPE_UNIT, Claim, resolve,
@@ -347,12 +348,12 @@ check("...and the shipped behaviour really was the other one, so the line "
       "above is not vacuous: an equal split of 1500 W is 750/750, and 750 W is "
       "what a pack at its cut-out was being told to produce",
       _r_now.shares == {A: 750, Bee: 750})
-_plan_a = next(p for p in _r_opt.allocation.plans if p.unit == A)
+_plan_a = first((p for p in _r_opt.allocation.plans if p.unit == A), "no plan for A")
 print(f"    {_plan_a.explain()}")
 check("...and the RECORD says why, in the line an operator is already reading. "
       "`UnitPlan.within_envelope` is asked rather than assumed, and SAFETY-28's "
       "write gate refuses a record that contradicts itself",
-      _plan_a.within_envelope and _plan_a.share_w == 0
+      present(_plan_a) and _plan_a.within_envelope and _plan_a.share_w == 0
       and _plan_a.hi == 0.0 and _r_opt.allocated)
 check("a pack at 100 % is not allocated a CHARGE either, and the sibling takes "
       "the whole of it - the same sentence in the other direction",
@@ -477,12 +478,12 @@ check("...and the two halves are separated from EACH OTHER as well: on a pack "
       "grades the ENVELOPE. Case three - both packs with room, nothing closed - "
       "is the one that can only be the WEIGHTS",
       _env_only.shares == {A: 0, Bee: 1500}
-      and _broken[2][1] != _broken[2][2])
+      and len(_broken) > 2 and _broken[2][1] != _broken[2][2])
 check("...and the third case is the one that isolates the WEIGHTS from the "
       "ENVELOPE: both packs have room, no interval is closed, nothing is "
       "refused - and the split still moves from 500/500 to 97/903 because the "
       "energy headroom says so",
-      _broken[2][1] == {A: 97, Bee: 903} and _broken[2][2] == {A: 500, Bee: 500})
+      nth(_broken, 2)[1] == {A: 97, Bee: 903} and nth(_broken, 2)[2] == {A: 500, Bee: 500})
 
 
 # ==============================================================================
@@ -1156,7 +1157,7 @@ check("⚠️ MAIN.PY ACTUALLY PASSES `weights=`, AND IT PASSES THE METHOD RATHE
 # reads the allocation's own `unmet_w`, is EDGE-TRIGGERED against the previous
 # cycle's value, and logs. What it does NOT grade is the sentence it logs or
 # that a real cycle reaches it; that is stated here rather than implied.
-_cycle_src = next(
+_cycle_src = first(
     f for cls in ast.walk(ast.parse(
         (Path(__file__).resolve().parent / "app" / "main.py")
         .read_text(encoding="utf-8")))