re: the 59-of-131 arsenal question is closed -- an item names a hardpoint

An Arsenal item does not reference a Weapon record.  It references a
Turret_NNN HARDPOINT SLOT on the player craft's own unit table, and the
slot is what carries the WeaponID.  Three hops:

  Arbalest_155KG.PlayerWeapon -> Turret_050  (a slot on
  UN_f001_TCAF_DeltaSaber_T_Player) -> .WeaponID ->
  Weapon_DSaber_P_wep_50_Cannon

Controls, both in the same loop: 0/59 distinct PlayerWeapon values are a
Weapon.ID; 59/59 are a Turret_NNN slot id; the full chain lands on a
Weapon.ID 59/59.  WingmanWeapon resolves identically.  The WEAPONS
roster's 59 = 55 item names + 4 empty-slot sentinels.

Wingmen fly a cheaper gun: following the same 59 slots across craft
variants, the _Player tables give each item its own weapon record (59
distinct) while the AI tables collapse all 59 onto 10 generic classes.
That is most of the 131.

Upgrades yesterday's 'hardpoint catalogue' reading from 21 to adopted,
proved from an independent file, and corrects its '10 distinct WeaponID'
figure -- that was the AI variant, not the player's.

Also adds an __main__ guard to unit_substructures.py so importing
pak_entries from it does not run its report; its artefact is unchanged
and still byte-identical.

docs/re/structures/unit-substructure-records.md

@@ -94,11 +94,16 @@ declared=1  records=2    x1   UN_e001_ADAN_Elan_EX4
 declared=8  records=9    x1   UN_e107_ADAN_AAFrigate_EX4
 ```
 
-🟡 The reading — **not adopted**: on the player craft the `Turret_NNN` list is
-a *hardpoint catalogue* and `TurretCount 4` is how many mount at once. It fits
-(63 slots, all `Frame=GN_mnt`, all `IsAuto=No`, 10 distinct `WeaponID`s across
-them, and the tutorial variants carry a cut-down 5) but nothing here shows the
-selection. The two `+1` warship/craft cases are unexplained.
+✅ **ADOPTED the next day** — on the player craft the `Turret_NNN` list is a
+*hardpoint catalogue* and `TurretCount 4` is how many mount at once. The
+Arsenal table proves it from an independent file: **59/59 of its items name a
+`Turret_NNN` slot in `PlayerWeapon`**, see
+[arsenal-item-weapon-chain](arsenal-item-weapon-chain.md). The two `+1`
+warship/craft cases are still unexplained.
+
+⚠️ The "10 distinct `WeaponID`s" measured here is the **AI** variant
+`UN_f001_TCAF_DeltaSaber_T`. The `_Player` variants give the same 59 slots
+**59 distinct** weapon records — wingmen fly a collapsed 10-class set.
 
 ## 🧪 Control 2 — turret weapons resolve into the weapon datasheet