How to query multiple tables from different buckets with inner join?

**Describe the issue**
In InfluxDB 3.4, attempting to perform an INNER JOIN on tables that originate from different buckets fails. This limits the ability to perform cross-bucket analysis, which is especially important for users with data logically separated by bucket (e.g., metrics and events).

Steps to reproduce

Create two buckets: bucketA and bucketB

Write data into each (e.g., cpu data in bucketA, and alerts in bucketB)

Attempt the following SQL-like query:

```
SELECT *
FROM bucket_1.cpu a
INNER JOIN bucket_2.alerts b
ON a.host = b.host AND a.time = b.time
```

Query fails or returns errors.

**Expected behavior**
The join should return rows where host and time match across the two tables, even if they come from different buckets.

**Actual behavior**

The query either fails with a syntax or execution error
`Query execution failed: API response error: "query error: error while planning query: Error during planning: table 'public.bucket_1.cpu' not found"`

No clear documentation that this use case is unsupported

**Environment**

InfluxDB version: 3.4

Query language: SQL from both Explorer UI and HTTP API

The issue names no source files or tests. Start by reproducing the cross-bucket INNER JOIN through the Explorer UI or HTTP API and inspect the planner error; trace how table names are resolved. Done means matching rows can be returned across buckets, with coverage for the reported query or a clear documented limitation.

Written by the indexing model from the issue text.