re: the disc ships the unit datasheet's own SCHEMA (and 文字列 was not a placeholder)

This corrects the previous commit. 文字列 is not a developer's leftover: it is
one member of a six-word Shift-JIS TYPE vocabulary, and the records carrying it
are a machine-readable schema for the unit datasheet.

The whole non-ASCII population on the disc is 6 distinct values out of 99328 -
0 of 3496 record names and 0 of 12173 field names - and all six are type words:

  文字列              string                366 uses
  NS_"文字列"         NS_ string             12
  整数 / 整数値        integer            66 / 6
  浮動小数値           floating-point value  504
  浮動小数値[0〜1]     float in [0,1]         36

990 type-valued fields. So the reader defect noted last time is real but bounded
to these six strings, and name_hash re-encodes Latin-1 byte-for-byte, so hashing
was never affected.

They sit in 15 records x 6 GP_MAIN_GAME_* paks = 90 instances, i.e. 15 records
with ONE user. The names are exactly the unit substructure family, and six carry
a literal wildcard: Turret_???, Hatch_???, Bridge_???, Thruster_???,
ShieldGenerator_???, Versatile_???, and NS_*. ??? is the numeric-suffix wildcard
at record AND field level - Turret_??? is the schema for Turret_000..00N, and
inside it CannonFrame_??? / MuzzleFrame_??? stand for the numbered slots.

Where a field's type is an enumeration the schema holds an EXAMPLE value instead
of a type name: Yes for the five booleans, Vessel for Generic.Type (the 43
Craft + 71 Vessel split), Ship_ for the ID prefix convention. Maneuver is the
one fully-typed record, 34 of 34. Every ResistanceTo* and every Color_* channel
is declared FLOAT[0..1] - normalised by declaration, matching the sampled values
in unit-datasheet-static. Generic.NozzleSpec_??? has its own type NS_"文字列"
and NS_* is a record, so the nozzle spec is a nested sub-schema.

Control separates schema from data cleanly: the _??? records and NS_* exist ONLY
as schema, 6 of 6 instances typed, while the eight real substructure names are
typed in 6 instances and untyped in the rest - Generic 6 of 3651, the others
6 of 684 each.

Turret_??? carries the game's own typo NomalModel beside DamagedModel.

This gives the port an authoritative field-type table: types the disc declares,
rather than types inferred from sampled values.

New artefact with its regenerator: tools/re-capture/datasheet_schema.py ->
docs/re/data/datasheet-schema.txt. All fifteen existing artefacts byte-identical.

tools/re-capture/datasheet_schema.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+"""The unit datasheet's own schema, as shipped on the disc.
+
+Each GP_MAIN_GAME_*.pak carries 15 IDXD records whose field VALUES are Japanese
+type names rather than data -- Shift-JIS, and the only non-ASCII strings on the
+whole disc. Records whose name ends '_???' (and 'NS_*') are wildcards standing
+for the numbered family, e.g. Turret_??? for Turret_000..Turret_00N.
+
+Where a field's type is an enumeration the schema holds an EXAMPLE value
+instead of a type name ('Yes' for a boolean, 'Vessel' for Generic.Type).
+
+Regenerates docs/re/data/datasheet-schema.txt.
+"""
+import glob, os, sys
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+from unit_substructures import pak_entries
+import unitgroup as U
+
+# the six type names, held as latin-1 (how unitgroup.py hands strings back)
+TYPES = {
+    '\x95\xb6\x8e\x9a\x97\xf1':                          'STRING',
+    'NS_"\x95\xb6\x8e\x9a\x97\xf1"':                     'NS_STRING',
+    '\x90\xae\x90\x94':                                  'INT',
+    '\x90\xae\x90\x94\x92l':                             'INT_VALUE',
+    '\x95\x82\x93\xae\x8f\xac\x90\x94\x92l':             'FLOAT',
+    '\x95\x82\x93\xae\x8f\xac\x90\x94\x92l[0\x81`1]':    'FLOAT[0..1]',
+}
+
+def main():
+    pak = sorted(glob.glob('/work/sylph_extract/**/GP_MAIN_GAME_D.pak', recursive=True))
+    if not pak:
+        print('disc not mounted; nothing to do'); return
+    out = {}
+    for h, b in pak_entries(pak[0]):
+        if b[:4] != b'IDXD':
+            continue
+        try:
+            recs = U.parse(b)
+        except Exception:
+            continue
+        for r in recs:
+            if any(v in TYPES for t, f, v in r['fields']):
+                out[r['squadron']] = r['fields']
+    print('the unit datasheet schema shipped in GP_MAIN_GAME_*.pak')
+    print('%d schema records; identical in all six paks (x6 = one user)' % len(out))
+    print()
+    for name in sorted(out):
+        fields = out[name]
+        typed = sum(1 for t, f, v in fields if v in TYPES)
+        print('=== %s (%d fields, %d typed) ===' % (name, len(fields), typed))
+        for t, f, v in sorted(fields, key=lambda x: (x[1] or '')):
+            print('   %-28s %s' % (f, TYPES.get(v, 'example: ' + repr(v))))
+        print()
+
+if __name__ == '__main__':
+    main()