data_diff: fuzzy column-name suggestions on errors

Flagged during v0.5.22 release review (End User persona).

When a user passes a misspelled column (`key_columns=['ordr_id']`), the tool surfaces the raw driver error via `SQL execution failed for task : `. Drivers like ClickHouse return cryptic messages (`Code: 47. DB::Exception: Missing columns: 'ordr_id'`).

Since we already run `DESCRIBE TABLE` / `information_schema` for auto-discovery (when `extra_columns` is omitted), we have the full column list available. On error we should:

1. Match driver error patterns (`Missing column`, `Unknown column`, `column not found`)
2. Pick closest match via Levenshtein
3. Append `Did you mean: 'order_id'?`

File: `packages/opencode/src/altimate/native/connections/data-diff.ts` ~L894

Deferred because: requires wiring discovery results into the error path — meaningful refactor, not a quick win.