dbt adapter startup in read-only and lineage tools #1683

Read-only tools can start the dbt adapter, and dbt_lineage waits on adapter startup it cannot use.

Items

• Read-only sql_execute can start the dbt adapter through workspace precedence #1654: Read-only sql_execute can start the dbt adapter through workspace precedence; propagate read-only context and assert zero adapter starts.
• dbt_lineage waits 120 s for a dbt adapter that doesn't start when writes are allowed #1666: dbt_lineage waits 120 s for an adapter that does not start when writes are allowed; skip unsupported startup.
• dbt_lineage: misleading hints for a column or an unknown model #1668: dbt_lineage gives misleading hints for a column or an unknown model; validate inputs and distinguish unknown models from corrupt manifests.

The linked issues hold the original reports and reproductions. Most are closed in favor of this tracker; any child with an open fix PR stays open until that PR lands.