fix(sqlite-proxy): handle undefined/empty rows in get() method

[claygeo]

Bug

Fixes #5461

When using drizzle-orm/sqlite-proxy, the get method returns { id: undefined } instead of undefined when no matching row exists. This happens because:

1. The AsyncRemoteCallback type declares rows: any[] for all methods, so proxy implementers naturally return { rows: [] } for empty results
2. An empty array [] is truthy, so mapGetResult() treats it as a valid row and maps it to an object with all fields set to undefined

Native SQLite drivers (better-sqlite3, bun:sqlite) return undefined from stmt.get() when no row matches. The sqlite-proxy driver should match this behavior.

Fix

• Type fix: Updated AsyncRemoteCallback and AsyncBatchRemoteCallback return types from { rows: any[] } to { rows: any[] | undefined }, allowing proxy implementers to return undefined for get with no results
• Runtime guard: Added normalization in get() to treat empty arrays as undefined, so both { rows: undefined } and { rows: [] } correctly produce undefined
• Batch guard: Fixed extractRawGetValueFromBatchResult to use optional chaining (rows?.[0]) instead of non-null assertion (rows![0]) to handle undefined rows safely
• Tests: Added unit tests covering all three cases (undefined rows, empty array rows, valid row)

Verification

All 565 existing tests pass. TypeScript compilation clean. New tests:

• get() returns undefined when callback returns { rows: undefined } ✓
• get() returns undefined when callback returns { rows: [] } ✓
• get() returns mapped row when callback returns valid result ✓