Validate ADL 2.4 at-coded archetypes

[MattijsK]

Fixes #791

Validate ADL 2.4 at-coded archetypes

Summary

Teaches the archetype validator to validate ADL 2.4 at-coded archetypes —
those whose structural node identifiers use the at prefix (e.g. at0000,
at0000.1) instead of id (id1, id1.1). Builds on the existing ADL 2.4
grammar (#659) and ADL 1.4 → ADL 2.4 at-coded converter (#658); this PR makes the
converter's output (and hand-written at-coded archetypes) pass validation,
including flattening and specialization.

Behaviour / configuration

A new ArchetypeValidationSettings.nodeIdCodeSystemValidation option controls which
node-id code system is accepted:

Value	Meaning
ID_CODED (default)	Only id-coded archetypes — fully backwards compatible
AT_CODED	Only at-coded archetypes
AUTO_DETECT	Detect the code system from the root node id and validate the rest against it

New rule: an archetype must use a single, consistent node-id code system, and
it must match the configured/detected one. Violations (mixed systems, or wrong
system for the configuration) are reported via a new error type
INVALID_NODE_ID_CODE_SYSTEM.

Changes

• NodeIdCodeSystemValidation enum + setting (default ID_CODED).
• ArchetypeValidationBase: expectsAtCodedNodeIds() resolver (auto-detect from
  root prefix) and a code-system-aware code-format check.
• CodeSystemValidation (new, phase 0): enforces the single/consistent code-system rule.
• BasicChecks: root-node pattern is code-system-aware (at0000(.1)* vs id1(.1)*).
• CodeValidation / BasicTerminologyValidation: terminology lookups and
  code-format/term-binding checks no longer assume the id prefix.
• AOMUtils (codesConformant, pathAtSpecializationLevel): accept the
  zero-padded codes at-coded ADL 2.4 retains from ADL 1.4 (uses isValidADL14Code,
  a strict superset of isValidCode, so id-coded behaviour is unchanged). This is
  what makes at-coded flattening and specialization validation work.
• ErrorType.INVALID_NODE_ID_CODE_SYSTEM added.
• i18n: English/Dutch messages for the new strings.

Tests

• AtCodedArchetypeValidationTest (13 tests): at-coded passes under AT_CODED /
  AUTO_DETECT and is rejected under the default ID_CODED (incl. via the no-settings
  default validator); id-coded vice-versa; mixed systems rejected (both AUTO_DETECT
  and explicit modes); malformed at-coded root; and a specialized at-coded archetype
  that validates and flattens end-to-end (OBSERVATION + CLUSTER fixtures).
• AOMUtilsTest.codesConformant: direct unit test of the core conformance change
  (id-coded, zero-padded at-coded, and prefix-collision non-conformance).

Compatibility & scope notes

• Default is ID_CODED, so existing behaviour is unchanged; full :aom/:tools
  suites pass.
• VARCN is retained for the root-node-form check (with an at-coded message variant);
  the new code-system-consistency rule uses the dedicated INVALID_NODE_ID_CODE_SYSTEM.
• A few seldom-used helpers (ArchetypeTerminology.idCodes(),
  hasIdCodeInAllLanguages()) still assume id-coded forms but aren't on the validation
  path; can be revisited if at-coded OPT generation needs them later.

[codecov]

Codecov Report

❌ Patch coverage is 87.71930% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.33%. Comparing base (73cb5e5) to head (79d3b30).

Files with missing lines	Patch %	Lines
...ypevalidator/validations/CodeSystemValidation.java	88.00%	1 Missing and 2 partials ⚠️
...ie/archetypevalidator/ArchetypeValidationBase.java	75.00%	0 Missing and 2 partials ⚠️
...main/java/com/nedap/archie/aom/utils/AOMUtils.java	50.00%	0 Missing and 1 partial ⚠️
...archetypevalidator/validations/CodeValidation.java	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                  Coverage Diff                  @@
##             adl_2.4_support     #799      +/-   ##
=====================================================
+ Coverage              72.28%   72.33%   +0.04%     
- Complexity              7233     7260      +27     
=====================================================
  Files                    680      682       +2     
  Lines                  23419    23467      +48     
  Branches                3795     3804       +9     
=====================================================
+ Hits                   16928    16974      +46     
  Misses                  4753     4753              
- Partials                1738     1740       +2     

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