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This pull request was authored by a coding agent.

📝 Summary

• A column reference such as "my.table".id can resolve against my.table when both tables occur in a query, producing a false unknown-column warning or missing an invalid column.
• Keep database, schema, and table qualifier segments separate through source matching. Single-identifier aliases retain precedence, including aliases that contain dots.
• Cover both directions of the quoted-name collision with valid and invalid columns, and require parser success so unsupported syntax cannot silently pass the cases. This follows up the existing limitation identified in #221.

📋 Pre-Review Checklist

• For large changes, or changes that affect the public API: this change was discussed or approved through an issue, on Discord, or the community discussions (Please provide a link if applicable).
• Any AI generated code has been reviewed line-by-line by the human PR author, who stands by it.
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✅ Merge Checklist

• I have read the contributor guidelines.
• Documentation has been updated where applicable, including docstrings for API changes.
• Tests have been added for the changes made.

Written by gpt-6 on Codex

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	93.67%	1717 / 1833
🔵	Statements	93.76%	1774 / 1892
🔵	Functions	94.77%	236 / 249
🔵	Branches	87.58%	1383 / 1579

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
src/sql/semantic-diagnostics.ts	95.75%	88.38%	100%	95.65%	162, 228, 287, 380, 404, 425, 449, 594-596, 630, 664

Generated in workflow #942 for commit 8f054ea by the Vitest Coverage Report Action

[cubic-dev-ai]

All reported issues were addressed across 2 files

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