SQL parser: ORDER BY on a bare table alias produces an empty column name (dangling qualifier)

[fupelaqu]

Symptom

When an ORDER BY identifier collides with a table alias — e.g.

SELECT e.name FROM emp e ORDER BY e

GenericIdentifier.update (sql/src/main/scala/app/softnetwork/elastic/sql/package.scala, alias-split logic ~L1224-1234) splits the identifier into name = "" and tableAlias = Some("e"). The reconstructed SQL then contains a dangling qualifier (ORDER BY e.); before the #158 fix it rendered ORDER BY ASC (empty name). Either way the statement is silently malformed instead of being rejected.

Scope

• Pre-existing bug, discovered during the REPL JOIN + ORDER BY fails: qualifier lost in AST→SQL reconstruction ('Ambiguous column') #158 code review (adversarial pass); NOT introduced by REPL JOIN + ORDER BY fails: qualifier lost in AST→SQL reconstruction ('Ambiguous column') #158 — the empty-name split predates it.
• Affects any clause going through the alias-split path, ORDER BY being the observable one.

Proposed fix

Reject the split in GenericIdentifier.update when the remaining column name is empty (validation error such as "Column name expected after table alias 'e'"), instead of manufacturing an empty identifier.

References

• Deferred review finding in story bug-158 (_bmad-output/implementation-artifacts/bug-158-repl-join-order-by-qualifier.md, Review Findings)
• Related: REPL JOIN + ORDER BY fails: qualifier lost in AST→SQL reconstruction ('Ambiguous column') #158 (FieldSort qualifier round-trip fix)