**Steps to reproduce:**
* Install the **Accounting** module.
* Unhide the **Start Date** and **End Date** fields on invoice lines.
* Create and post a customer invoice with deferred dates.
* Go to **Accounting → Reports → Deferred Revenue Report**.
* Add an annotation to a deferred revenue line by clicking the **annotate** from three dots next to the account.
* Export the report in **XLSX** format.

**Observed behavior:**
* The export fails with a server error: `UnboundLocalError: cannot access local variable 'annotations_x_offset' where it is not associated with a value`

**Cause:**
* The variable `annotations_x_offset` is assigned inside the `for header_level_index, header_level in enumerate(options['column_headers'])` loop, which writes the "Annotations" column header for each header level.
* The Deferred Revenue Report produces an empty `column_headers` list, so the loop body never executes and `annotations_x_offset` is never assigned.
* When the code later tries to write annotation data for each report line, it references the unassigned variable, causing Python to raise `UnboundLocalError`.

**Fix:**
* Introduce a boolean flag `annotations_header_written = False` before the header loop to explicitly track whether the "Annotations" column header has already been written.
* Inside the header loop, set `annotations_header_written = True` after writing the header.
* After writing all individual column headers (where `x_offset` already points to the first free column after all data columns), add a fallback: if `report_annotations` is set but `annotations_header_written` is still `False`, assign `annotations_x_offset` from the current `x_offset` and write the "Annotations" header.

opw-6354473

Forward-Port-Of: odoo/enterprise#127840
Forward-Port-Of: odoo/enterprise#122768

When the AI agent switched from another view to a pivot view, the pivot view could crash or open without any active measures.

The AI controller patch applies the agent's adjustments upon receiving the `APPLY_AI_ADJUST_MODEL` bus event. However, the event could be processed while the pivot model was still executing `_loadData()`.

In that case, the following sequence occurred:

* `_loadData()` started and awaited.
* The controller patch was executed.
* The patch called `toggleMeasures()`.
* `toggleMeasures()` waited for `_loadData()` to complete.
* `_loadData()` finished and updated the metadata with the available measures.
* `toggleMeasures()` resumed and wrote back the metadata snapshot it had taken before waiting.

Since `toggleMeasures()` operates on a snapshot of the metadata, the measures populated by `_loadData()` were lost when the snapshot replaced the current metadata, leaving the pivot model without its `measures` metadata and causing the view to crash.

Prevent this race condition by waiting for the pivot model initialization to complete before applying the AI adjustments.

Also preserve the default active measures when the AI agent does not explicitly request any measures instead of clearing them and opening an empty pivot view.

task-6384368