[BUG]: SQLite pull crashes on any expression index, because .on() doesn't filter the keys the line above it does

### Report hasn't been filed before.

- [x] I have verified that the bug I'm about to report hasn't been filed before.

### What version of `drizzle-orm` are you using?

1.0.0-rc.4

### What version of `drizzle-kit` are you using?

1.0.0-rc.4

### Other packages

better-sqlite3@13.0.3, node:sqlite (Node 24.17.0)

### Describe the Bug

`pull` fails on any SQLite index over an expression. In `createTableIndexes` (`dialects/sqlite/typescript.ts`) the generated-name line filters expression keys out and the `.on()` line below it doesn't:

```ts
const columnNames = it.columns.filter((c) => !c.isExpression).map((c) => c.value);
...
statement += `.on(${it.columns.map((it) => `table.${withCasing(it.value, casing)}`).join(', ')})`;
```

`value` is null for an expression key. `introspect.ts` builds the column as `{ value: it.column, isExpression: it.cid === -2 }`, and `ii.name` from `pragma_index_info` is NULL exactly when `cid` is -2, so `withCasing(null)` throws. The row type says `value: string`, which is why tsc doesn't see it.

Smallest case:

```sql
CREATE TABLE t (id INTEGER PRIMARY KEY, code TEXT NOT NULL);
CREATE INDEX i ON t (lower(code));
```

```
[✓] 1 tables fetched
[✓] 2 columns fetched
[✓] 1 indexes fetched
[✓] 0 foreign keys fetched
[✓] 0 check constraints fetched
[✓] 0 views fetched
Failed to connect to or introspect the SQLite database
```

The real error, from logging the `catch` that produces that last line:

```
TypeError: Cannot read properties of null (reading 'camelCase')
at withCasing$2 (bin.cjs:155408:58)
at bin.cjs:155593:56
at Array.map ()
at createTableIndexes$2 (bin.cjs:155593:35)
at ddlToTypeScript$2 (bin.cjs:155457:18)
at handle$7 (bin.cjs:155688:14)
```

Which shapes hit it, same table:

| index | result |
| --- | --- |
| `CREATE INDEX i ON t (lower(code))` | crash |
| `CREATE UNIQUE INDEX i ON t (lower(code))` | crash |
| `CREATE INDEX i ON t (lower(code), id)` | crash |
| `CREATE UNIQUE INDEX i ON t (lower(code), id)` | `unexpected unique index 'i' with expression value: ...` |

Only the last row is #6159, and #6171 fixes that one in `fromDatabase`. The other three never reach that loop.

Filtering expression keys out of `.on()` stops the crash, but it drops the index to its plain columns, and to nothing at all for the first two. `IndexColumn` is `SQLiteColumn | SQL`, so the shape that round-trips is:

```ts
index("i").on(sql`lower(code)`)
```

The expression text isn't in the row to write that with, though. `pragma_index_info` gives the null and nothing else, so it means reading the index's own DDL, which is the same correlated subquery on `sqlite_master` that #6236 is adding for the partial `WHERE`.

Separate, but it's what made this expensive to find: the `catch` around SQLite pull rewrites any untyped error into `Failed to connect to or introspect the SQLite database` and lists `better-sqlite3`, `bun`, `@libsql/client`, `@tursodatabase/database`, `node:sqlite`. The driver had connected and printed six fetch lines directly above. Letting the error through, or a flag that does, would save the bisect.

Same on 1.0.0-rc.5-ab785fc. `0.31.10` doesn't crash, but writes `index("i").on()` with no arguments, which doesn't typecheck against `on(...columns: [IndexColumn, ...IndexColumn[]])`, so the null wants handling on that line either way. The same null reaching the casing function is open for MySQL as #4499 and #5546 (PR #5548). A guard in `withCasing` covers the crash in every dialect, but each one finds the expression text somewhere different, so keeping the index is separate work.