Add header filtering support

[Sytten]

No description provided.

[Copilot]

Pull request overview

Adds HTTPQL request header filtering so queries can match on header name/value, including a shorthand bracket form that expands to an AND between header-name equality and header-value filtering.

Changes:

• Extend Rust + JS grammars/parsers to support req.header.name|value.<stringExpr> and req.header["<Name>"].<stringExpr>.
• Add request header primitives + serialization support in both Rust and JS implementations.
• Add AST golden tests for the explicit and shorthand header syntaxes.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/httpql/ast/20/input.httpql	New golden input covering explicit req.header.name + req.header.value filtering.
tests/httpql/ast/20/output.ast	Expected canonical AST string for explicit header filtering.
tests/httpql/ast/21/input.httpql	New golden input covering shorthand req.header["..."] syntax.
tests/httpql/ast/21/output.ast	Expected canonical AST string for shorthand syntax (expanded to AND).
rust/httpql/src/primitives.rs	Adds request header clause primitive and display formatting (`req.header.name
rust/httpql/src/parser.rs	Parses header filtering, including shorthand expansion into an and Query.
rust/httpql/src/lib.rs	Adds Rust golden test cases 20 and 21.
rust/httpql/httpql.pest	Extends Pest grammar with header field/subfields and bracket syntax.
js/httpql/src/primitives.ts	Adds ClauseRequestHeader to the JS AST types.
js/httpql/src/serialize.ts	Serializes request header name/value filters.
js/httpql/src/deserialize/clause.ts	Adjusts request clause deserialization to return a full Query (needed for shorthand AND expansion).
js/httpql/src/deserialize/clause.request.ts	Implements header long-form and shorthand parsing (shorthand expands to AND).
js/httpql/httpql.grammar	Extends Lezer grammar with header field/subfields and bracket syntax.
js/httpql/src/parser/parser.ts	Regenerated Lezer parser output to reflect grammar changes.
js/httpql/src/parser/parser.terms.ts	Regenerated term IDs/names to include new header/bracket tokens.
js/httpql/src/index.spec.ts	Adds JS golden test cases 20 and 21.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.