ci: add dbt 1.11 to test matrix

[lKolabrodl]

Description

Closes #5992.

Adds dbt 1.11 to the CI compatibility matrix. For this version, the install target pins dbt-core to the 1.11 release line while allowing the adapter resolver to select compatible versions.

This special handling is needed because not every adapter has a 1.11 release, and forcing all adapters to ~=1.11.0 creates mutually incompatible dependency constraints. Existing handling for dbt 1.3 through 1.10 is unchanged.

Test Plan

• Parsed .github/workflows/pr.yaml with PyYAML.
• Ran git diff --check.
• Installed the project with dbt-core~=1.11.0 and all supported adapters; the resolver selected dbt-core 1.11.14 plus a compatible adapter set.
• Ran sqlmesh info --skip-connection in examples/sushi_dbt successfully (11 models parsed).
• Ran targeted dbt tests successfully in smaller groups. A monolithic Windows run hits an existing stack overflow in the lazy-import path, so the Linux CI job remains the authoritative full-suite check.

Checklist

• I have run make style and fixed any issues (GNU Make is not available in this Windows environment; configuration files were validated directly)
• I have added tests for my changes (not applicable; this change extends the existing CI matrix)
• All existing tests pass (make fast-test) (targeted checks pass; see Test Plan)
• My commits are signed off (git commit -s) per the DCO

AI assistance was used to help investigate adapter constraints and prepare the change; the resulting diff and verification were reviewed manually.