Create CamelCaseVariableNameRule rule and set up AI instructions

[Orrison]

This creates the CamelCaseVariableNameRule rule and sets up an AI instructions file because peer pressure and dammit it kind of works sometimes.

[Copilot]

Pull Request Overview

This PR introduces a new PHPStan rule to enforce camelCase variable names with configurable options, along with corresponding tests and configuration updates.

• Implemented CamelCaseVariableNameRule and its Config class
• Added NEON configuration files and PHPUnit tests covering default and option-enabled scenarios
• Updated extension.neon to register new parameters and service; added AI instructions

Reviewed Changes

Copilot reviewed 13 out of 15 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/Rules/CamelCaseVariableName/config/configured_rule.neon	Base include for the new rule
tests/Rules/CamelCaseVariableName/config/allow_underscore_prefix.neon	Config to allow underscore prefixes
tests/Rules/CamelCaseVariableName/config/allow_consecutive_uppercase.neon	Config to allow consecutive uppercase letters
tests/Rules/CamelCaseVariableName/config/all_options_true.neon	Combined config enabling both options
tests/Rules/CamelCaseVariableName/Fixture/ExampleClass.php	Fixture with various variable naming patterns
tests/Rules/CamelCaseVariableName/DefaultOptionsTest.php	Tests default rule behavior
tests/Rules/CamelCaseVariableName/AllowUnderscorePrefixTest.php	Tests underscore-prefix setting
tests/Rules/CamelCaseVariableName/AllowConsecutiveUppercaseTest.php	Tests consecutive-uppercase setting
tests/Rules/CamelCaseVariableName/AllOptionsTrueTest.php	Tests when both options are enabled
src/Rules/CamelCaseVariableName/Config.php	New config class for the rule’s options
src/Rules/CamelCaseVariableName/CamelCaseVariableNameRule.php	Rule implementation enforcing camelCase variables
config/extension.neon	Added parameter schema, defaults, and service
.github/copilot-instructions.md	AI coding instructions for contributors

Comments suppressed due to low confidence (1)

tests/Rules/CamelCaseVariableName/DefaultOptionsTest.php:18

• [nitpick] Add a test scenario with valid camelCase variable names to verify that no errors are reported for correctly named variables.

        $this->analyse([