feat: support checking out a version on a branch (#3504)

### Description

Stacked on #3490. Adds an optional version to branch checkout across the
Rust core and the Python and TypeScript SDKs, so you can open a specific
version on a branch ("version V of branch B"), not just the branch's
latest version

Rust

```rust
// Open version 3 of branch "exp" (a read-only view): check out from an
// existing table, or open it directly from the connection.
let exp_v3 = table.checkout_branch("exp", Some(3)).await?;
let exp_v3 = db.open_table("items").branch("exp").version(3).execute().await?;
// checkout_latest re-attaches to the branch's writable HEAD.
exp_v3.checkout_latest().await?;

// With no branch, a version opens main at that version.
let main_v3 = db.open_table("items").version(3).execute().await?;
```

Python

```python
# Open version 3 of branch "exp" (a read-only view): check out from an
# existing table, or open it directly from the connection.
branch_v3 = await table.branches.checkout("exp", version=3)
branch_v3 = await db.open_table("items", branch="exp", version=3)
# checkout_latest re-attaches to the branch's writable HEAD.
await branch_v3.checkout_latest()

# With no branch, a version opens main at that version.
main_v3 = await db.open_table("items", version=3)
```

TypeScript

```typescript
// Open version 3 of branch "exp" (a read-only view): check out from an
// existing table, or open it directly from the connection.
const branchV3 = await (await table.branches()).checkout("exp", 3);
const opened = await db.openTable("items", undefined, { branch: "exp", version: 3 });
// checkoutLatest re-attaches to the branch's writable HEAD.
await branchV3.checkoutLatest();

// With no branch, a version opens main at that version.
const mainV3 = await db.openTable("items", undefined, { version: 3 });
```

### Testing
- Added unit tests (Rust, Python sync + async, TypeScript):
branch-scoped resolution at a version number shared with `main` and with
another branch, read-only enforcement on a pinned handle,
`checkout_latest` recovery to the branch's HEAD, fork-point reads, and
the nonexistent-version/branch error paths.
- Ran smoke tests against the Python and TypeScript SDKs on local
machine.

nodejs/lancedb/connection.ts

@@ -90,6 +90,14 @@ export interface OpenTableOptions {
    * Reads and writes on the returned table operate in the branch's context.
    */
   branch?: string;
+  /**
+   * Open the table pinned to this version, producing a read-only view.
+   *
+   * Composes with {@link OpenTableOptions.branch}: when both are set, opens
+   * that branch at the version; otherwise opens `main` at the version. Call
+   * `checkoutLatest` to return to a writable state.
+   */
+  version?: number;
   /**
    * Configuration for object storage.
    *
@@ -489,9 +497,18 @@ export class LocalConnection extends Connection {
       options?.indexCacheSize,
     );
 
-    const table = new LocalTable(innerTable);
-    if (options?.branch != null) {
-      return (await table.branches()).checkout(options.branch);
+    let table: Table = new LocalTable(innerTable);
+    // "main" is the default branch, so treat it as no branch. On a real branch,
+    // scope and pin in one step (yielding "version V of branch B"); otherwise
+    // pin the version, if any, against main.
+    const branch =
+      options?.branch != null && options.branch !== "main"
+        ? options.branch
+        : undefined;
+    if (branch != null) {
+      table = await (await table.branches()).checkout(branch, options?.version);
+    } else if (options?.version != null) {
+      await table.checkout(options.version);
     }
     return table;
   }

nodejs/lancedb/table.ts

@@ -1290,9 +1290,15 @@ export class Branches {
     return new LocalTable(await this.#inner.create(name, fromRef, fromVersion));
   }
 
-  /** Check out an existing branch and return a handle scoped to it. */
-  async checkout(name: string): Promise<Table> {
-    return new LocalTable(await this.#inner.checkout(name));
+  /**
+   * Check out an existing branch and return a handle scoped to it.
+   *
+   * With `version` set, the returned handle is pinned to that version of the
+   * branch (a read-only, detached view); otherwise it tracks the branch's
+   * latest and stays writable.
+   */
+  async checkout(name: string, version?: number): Promise<Table> {
+    return new LocalTable(await this.#inner.checkout(name, version));
   }
 
   /** Delete a branch. */