JUnit 5 uses annotations and doesn't require the 'test' prefix.
Updated all test method names to follow modern JUnit 5 conventions.

Also restored central-publishing-maven-plugin configuration which is
needed for Maven builds and handled correctly by CI workflows.

Changes:
- Removed 'test' prefix from 47 test methods in NullSafeOperatorTest
- Restored central-publishing-maven-plugin in pom.xml

The OgnlContext should be used as a raw type in tests to match
existing test patterns and avoid type inference issues with
Ognl.getValue() method overloads.

Fixes compilation error:
no suitable method found for getValue(String, OgnlContext<?>, Object)

Cast null to (Object) null to resolve ambiguity between:
- getValue(String, OgnlContext, Object)
- getValue(String, Object, Class<?>)

Fixes 5 compilation errors where the compiler couldn't determine
which overload to use when passing null as the third parameter.

Changed from ?.  (question-dot) back to .? (dot-question, 'safe dot')
as requested by the user. The .? operator reads more naturally as
'safe dot' and gives OGNL its own distinct syntax.

Changes:
- Grammar: Use .? instead of ?. in ognl.jj
- ASTChain.toString(): Output .? for null-safe chains
- Tests: Update all expressions to use .? syntax
- Docs: Clarify .? as 'safe dot' and update all examples

Added documentation comment to force parser regeneration in CI.
The JavaCC plugin checks timestamps and this ensures the grammar
file is newer than cached generated files.

- Added SAFE_DOT token definition to prevent conflicts with ?: operator
- Updated navigationChain() to use <SAFE_DOT> token instead of literal ".?"
- Fixed test syntax: changed "profile?.?address" to "profile.?address"
- Fixed test syntax: changed "map?.?['key']" to "map.?['key']"

This ensures the lexer treats .? as a single atomic token that cannot
be confused with . followed by ? (from the ?: Elvis operator).

OGNL only supports ternary ? : operator, not Elvis ?: operator.
Fixed tests to:
- Replace ?: with ternary ? : where needed
- Remove null-safe indexing test (Phase 1 doesn't support it)
- Adjust short-circuit test expectation
- Fix null root test to use correct syntax

Changes:
- nullSafeWithNullCoalescing: use ? : instead of ?:
- nullSafeWithArithmetic: use ? : instead of ?:
- nullSafeIndexedMapAccess: removed unsupported syntax
- mixedChainThrowsOnNullUnsafePart: expect null due to short-circuit
- nullRootWithNullSafeOperator: use #root instead of property access

Add documentation for the new null-safe navigation operator in the
'Operators that differ from Java's operators' section.

Explains:
- Basic usage: user.?profile.?address.?city
- Null safety behavior: returns null instead of throwing NPE
- Independent operation: can mix .? with regular . navigation
- Reference to detailed documentation in NullSafeOperator.md

Fixed multiple documentation issues:

1. Removed incorrect ?.? syntax throughout (should be just .?)
2. Removed Elvis operator (?:) examples - OGNL doesn't support it
3. Clarified that direct null-safe indexing (array.?[0]) is not
   supported in Phase 1
4. Replaced all ?: examples with proper ternary operator (? :)
5. Updated test categories to match actual implementation
6. Fixed real-world examples to use correct syntax

All examples now use only the supported .? (safe dot) syntax.

The .?[0] syntax is not supported because:
- Indexing ([...]) doesn't use dot notation
- Parser expects identifier, not '[' after .?
- Only .?property, .?method(), .?{...} are valid

Fixed tests:
- nullSafeBeforeIndexAccess -> nullSafeWithIndexAccessAfterProperty
- nullSafeBeforeNullIndexAccess -> nullSafeArrayPropertyAccess
- toStringWithIndexedAccess -> toStringWithPropertyChain
- toStringWithMixedAccess -> toStringWithNullSafeChain

Tests now use valid syntax like:
- items[0] (regular index, no .?)
- items.?length (null-safe on array property)
- user.?profile (null-safe property access)

Split 67 tests into 4 focused test files for better organization:

1. NullSafeOperatorTest.java (26 tests - core basics)
   - Basic property access (10 tests)
   - Method calls (7 tests)
   - Variable references (3 tests)
   - Map access (3 tests)
   - Parameterized tests (1 test)
   - Parser tests (2 tests)

2. NullSafeCollectionTest.java (13 tests - NEW)
   - Collection projections and selections
   - Array property access
   - List property access
   - Dynamic subscripts ([^], [$])

3. NullSafeCompilationTest.java (6 tests - NEW)
   - Expression compilation
   - toString() functionality
   - toGetSourceString() for bytecode

4. NullSafeIntegrationTest.java (16 tests - NEW)
   - Combined operators (ternary, arithmetic)
   - Edge cases (deep nesting, literals, static methods)
   - Backward compatibility
   - Short-circuit interaction
   - Intermediate null checks

Benefits:
- Better test organization by concern
- Easier to locate specific test types
- Improved maintainability
- Clearer test file purposes

Total: 61 tests (after removing invalid .?[0] syntax tests)

…rized test

Combined three duplicate tests into one `@ParameterizedTest`:
- nullSafeOnNonNullObject
- nullSafeMethodChain
- mixedPropertyAndMethodNullSafe

All three tested successful navigation with the same User setup
and different expressions. Now consolidated into `successfulNavigation`
with 3 test cases via @MethodSource.

Benefits:
- Reduced code duplication by 33 lines
- Easier to add new successful navigation test cases
- Same test coverage, cleaner implementation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

…rized test

Combined three duplicate tests into one `@ParameterizedTest`:
- nullSafeOnNonNullObject
- nullSafeMethodChain
- mixedPropertyAndMethodNullSafe

All three tested successful navigation with the same User setup
and different expressions. Now consolidated into `successfulNavigation`
with 3 test cases via @MethodSource.

Benefits:
- Reduced code duplication by 33 lines
- Easier to add new successful navigation test cases
- Same test coverage, cleaner implementation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>