Refactor vCard validation and canonicalize VERSION handling

Move whole-card cardinality checks into overloaded validate helpers in
the vCard 3 and vCard 4 modules, and have readVCard invoke those
validators after parsing instead of hard-coding property checks in the
shared parser.

For vCard 3, validate property cardinality directly from propertyCardMap
and add regression coverage for duplicate single-cardinality properties.
For vCard 4, validate from propertyCardMap as well, while preserving
ALTID semantics for single-cardinality properties so alternate
representations remain valid and duplicate ungrouped properties are
rejected.

Rework VERSION handling to treat it as parser metadata rather than
stored card content. Parsing still requires exactly one canonical
VERSION line and rejects missing or duplicate occurrences, but parsed
cards no longer retain VC3_Version or VC4_Version objects in content.
Accessors and serializers continue to expose and emit the canonical
version for the concrete card type, which keeps parsed and
programmatically constructed cards on the same model.

Update the vCard 3 and vCard 4 test suites to cover the new validation
path, confirm VERSION is not persisted in content, and adjust fixture
expectations to match the canonical VERSION model.

AI-Assisted: yes
AI-Tool: OpenAI Codex / gpt-5.4 xhigh

tests/tvcard3.nim

@@ -1,4 +1,4 @@
-import std/[options, strutils, times, unittest]
+import std/[options, sequtils, strutils, times, unittest]
 import zero_functional
 
 import vcard
@@ -57,6 +57,7 @@ suite "vcard/vcard3":
       "BEGIN:vCard\r\n" &
       "VERSION:3.0\r\n" &
       "FN:Frank Dawson\r\n" &
+      "N:Dawson;Frank;;;\r\n" &
       "ORG:Lotus Development Corporation\r\n" &
       "ADR;TYPE=WORK,POSTAL,PARCEL:;;6544 Battleford Drive\r\n" &
       " ;Raleigh;NC;27613-3502;U.S.A.\r\n" &
@@ -71,6 +72,7 @@ suite "vcard/vcard3":
       "BEGIN:vCard\r\n" &
       "VERSION:3.0\r\n" &
       "FN:Tim Howes\r\n" &
+      "N:Howes;Tim;;;\r\n" &
       "ORG:Netscape Communications Corp.\r\n" &
       "ADR;TYPE=WORK:;;501 E. Middlefield Rd.;Mountain View;\r\n" &
       " CA; 94043;U.S.A.\r\n" &
@@ -104,6 +106,25 @@ suite "vcard/vcard3":
         "VERSION:3.0",
         "FN:John Smith"))
 
+  test "spec: parser rejects duplicate single-cardinality vCard 3 properties":
+    expect(VCardParsingError):
+      discard parseVCards(vcard3Doc(
+        "VERSION:3.0",
+        "FN:John Smith",
+        "N:Smith;John;;;",
+        "BDAY:2000-01-01",
+        "BDAY:2000-01-02"))
+
+  test "spec: VERSION is not stored as vCard 3 content":
+    let parsed = parseSingleVCard3(vcard3Doc(
+      "VERSION:3.0",
+      "FN:John Smith",
+      "N:Smith;John;;;"))
+
+    check:
+      parsed.version.value == "3.0"
+      parsed.content.countIt(it of VC3_Version) == 0
+
   test "spec: simple text values decode RFC 2426 escapes when parsing":
     let parsed = parseSingleVCard3(vcard3Doc(
       "VERSION:3.0",

tests/tvcard4.nim

@@ -1,4 +1,4 @@
-import std/[options, strutils, tables, unittest]
+import std/[options, sequtils, strutils, tables, unittest]
 import zero_functional
 
 import vcard
@@ -203,6 +203,7 @@ suite "vcard/vcard4":
       madeUpProp.value == "Sample value for my made-up prop."
 
   let cardWithAltBdayStr = testVCardTemplate % [(
+    "FN:Simon Perreault\r\n" &
     "BDAY;VALUE=text;ALTID=1:20th century\r\n" &
     "BDAY;VALUE=date-and-or-time;ALTID=1:19650321\r\n"
   )]
@@ -210,6 +211,14 @@ suite "vcard/vcard4":
   test "single-cardinality properties allow multiples with ALTID":
     check parseVCards(cardWithAltBdayStr).len == 1
 
+  test "single-cardinality properties reject multiples without ALTID":
+    expect(VCardParsingError):
+      discard parseVCards(testVCardTemplate % [(
+        "FN:Simon Perreault\r\n" &
+        "BDAY;VALUE=text:20th century\r\n" &
+        "BDAY;VALUE=date-and-or-time:19650321\r\n"
+      )])
+
   let hasAltBdays = cast[VCard4](parseVCards(cardWithAltBdayStr)[0])
 
   test "properties with cardinality 1 and altids return the first found by default":
@@ -222,6 +231,7 @@ suite "vcard/vcard4":
     check:
       hasAltBdays.content.len == 3
       hasAltBdays.bday.isSome
+      hasAltBdays.content.countIt(it of VC4_Version) == 0
 
     let allBdays = allAlternatives[VC4_Bday](hasAltBdays)
     check: