feat: computed expressions and expression-based updates

[flyon]

Summary

Properties in select() and update() now support expressions — you can compute values dynamically instead of just reading or writing raw fields.

• Computed fields in queries — chain methods like .strlen(), .times(), .ucase(), .year() on properties inside select() to derive new values on the fly
• Expression-based WHERE filters — filter using computed conditions (p.name.strlen().gt(5)), not just equality. Works on queries, updates, and deletes
• Computed updates — calculate new values from existing ones in update queries (p.age.plus(1)) instead of providing static values
• Expr module — standalone expressions that don't start from a property: Expr.now(), Expr.ifThen(), Expr.firstDefined()

// Compute derived fields
await Person.select(p => ({ name: p.name, nameLen: p.name.strlen(), ageMonths: p.age.times(12) }));

// Filter on computed values
await Person.select(p => p.name).where(p => p.age.gt(18));

// Update with expressions
await Person.update(p => ({ age: p.age.plus(1) })).for(entity);
await Person.update({ lastSeen: Expr.now() }).for(entity);

Also removes stale changesets already processed on dev, and extracts a shared createTraversalResolver factory from 4 duplicated traversal implementations.

Test plan

• 821 tests passing, 0 failures
• ExpressionNode unit tests (~65 cases), Expr module tests (~64), type tests (14)
• Golden SPARQL tests for expression SELECT, WHERE, and mutations
• TypeScript compiles clean

🤖 Generated with Claude Code