feat!: rename branch merge to cherry_pick (#3986)

This PR is a **breaking** rename of #3686.

merge reads like git merge w/ three-way, replay history, combine two
lines of work. That is not this API.

This call takes one additive change on a branch and lands it on main.
New column, including a blob column. Main's existing columns are not
rewritten. If it cannot land, you get `status="failed"` and
`diff.errors`, not a merge conflict to resolve.

Cherry-pick is terminology that aligns more with that.

```python
table = db.open_table("images")
table.branches.create("exp")
exp = table.branches.checkout("exp")

exp.add_columns({"tag": "cast('draft' as string)"})

diff = table.branches.diff("exp")
preview = table.branches.cherry_pick("exp", dry_run=True)
result = table.branches.cherry_pick("exp")

if result["status"] == "cherryPicked":
    print("landed at", result["mainVersionAfter"])
elif result["status"] == "failed":
    print(result["diff"]["errors"])
```

### Behavior

- Remote / Enterprise only. Local still NotSupported.
- HTTP 409 is not an exception. It is Ok with status="failed" and
diff.errors (CherryPickError).
- Unknown error / status codes still parse as Unknown.
- Requests are not retried. 409 is final and carries the body.
- Endpoint is POST /v1/table/{id}/branches/cherry_pick/.
- merge_insert and Table.merge are unchanged.

### Testing
- `cargo test -p lancedb --features remote diff_branch`
- `cargo test -p lancedb --features remote cherry_pick`
- `pytest python/python/tests/test_remote_db.py -k cherry_pick`
- node `remote.test.ts` diffs / cherry-picks path

docs/src/js/classes/Branches.md

@@ -37,6 +37,31 @@ latest and stays writable.
 
 ***
 
+### cherryPick()
+
+```ts
+cherryPick(fromBranch, dryRun): Promise<CherryPickResult>
+```
+
+Cherry-pick a branch onto main.
+
+Set `dryRun` to `true` to preview. A failed cherry-pick resolves
+with `status: "failed"` instead of throwing.
+
+#### Parameters
+
+* **fromBranch**: `string`
+    Branch to cherry-pick from.
+
+* **dryRun**: `boolean` = `false`
+    When true, only preview. Defaults to false.
+
+#### Returns
+
+`Promise`&lt;[`CherryPickResult`](../interfaces/CherryPickResult.md)&gt;
+
+***
+
 ### create()
 
 ```ts
@@ -112,28 +137,3 @@ List all branches, mapping name to branch metadata.
 #### Returns
 
 `Promise`&lt;`Record`&lt;`string`, [`BranchContents`](BranchContents.md)&gt;&gt;
-
-***
-
-### merge()
-
-```ts
-merge(fromBranch, dryRun): Promise<MergeBranchResult>
-```
-
-Merge a branch into main.
-
-Set `dryRun` to `true` to preview the merge. A rejected merge resolves
-with `status: "rejected"` instead of throwing.
-
-#### Parameters
-
-* **fromBranch**: `string`
-    Branch to merge from.
-
-* **dryRun**: `boolean` = `false`
-    When true, only preview the merge. Defaults to false.
-
-#### Returns
-
-`Promise`&lt;[`MergeBranchResult`](../interfaces/MergeBranchResult.md)&gt;