feat: parse instance data paths

[HassanAkbar]

fixes #3

[Copilot]

Pull request overview

This PR extends Lutaml::Path.parse to support model-instance path syntax (dot navigation plus optional bracketed filter expressions) while preserving the existing element path (::) parsing. It introduces new value objects for instance paths and filter-condition AST nodes, and updates the README and specs accordingly.

Changes:

• Add InstancePath and Step representations to support dot navigation and attaching parsed filter conditions to individual steps.
• Add a Condition AST (comparison/membership/existence/logical ops) and parsing rules with operator precedence and grouping.
• Improve round-tripping (to_s) and equality semantics for parsed paths; document the new behavior in the README.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
spec/lutaml/path_spec.rb	Adds extensive coverage for instance-path parsing, filter forms, precedence/grouping, round-trips, and immutability expectations.
README.adoc	Documents operator precedence, literal forms, filter-vs-charset rules, and clarifies instance paths are parse-only for now.
lib/lutaml/path/parser.rb	Extends grammar to support dot navigation and filter condition parsing with a token-aware “filter sniff”.
lib/lutaml/path/transformer.rb	Transforms parse trees into ElementPath/InstancePath, Step, and Condition nodes (but currently contains runtime-breaking transform bugs).
lib/lutaml/path/step.rb	Introduces Step to compose PathSegment + optional condition and render appropriately.
lib/lutaml/path/path_segment.rb	Preserves raw source for round-tripping and adds value equality/hash; unescapes \:: and \. into name.
lib/lutaml/path/instance_path.rb	Adds parse-only InstancePath with structured steps, conditions, to_s, and explicit match? NotImplementedError.
lib/lutaml/path/element_path.rb	Makes ElementPath inherit AbstractPath and adds to_s/value equality/hash.
lib/lutaml/path/condition.rb	Adds immutable, renderable filter-condition AST node types (AttributeRef, Value, Comparison, etc.).
lib/lutaml/path/abstract_path.rb	Adds a common base type holding only absolute?.
lib/lutaml/path.rb	Updates require order and ensures parse consistently raises ParseError (including for deep nesting via SystemStackError).

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[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.