Fix fill_tiled segfault

Reviewer's Guide by Sourcery

The PR fixes a segfault in the fill_tiled function by introducing a temporary layout and cell to handle fill operations. Instead of directly modifying the target cell during the filling process, the changes are first applied to a temporary cell and then transferred to the target cell in a controlled manner.

Sequence diagram for fill_tiled function changes

sequenceDiagram
    participant FillOperator
    participant temp_ly as Temporary Layout
    participant temp_tc as Temporary Cell
    participant top_cell as Top Cell
    participant fill_cell as Fill Cell

    fill_tiled->>FillOperator: Create FillOperator instance
    FillOperator->>temp_ly: Start changes
    FillOperator->>temp_tc: fill_region_multi or fill_region
    FillOperator->>temp_ly: End changes
    FillOperator->>temp_tc: Iterate each_inst
    temp_tc->>top_cell: Insert cell_inst_array
    fill_tiled->>FillOperator: insert_fill()
    FillOperator->>top_cell: Insert fill cell into regions

Class diagram for FillOperator changes

classDiagram
    class FillOperator {
        +list<kdb.Cell> filled_cells
        +kdb.Layout temp_ly
        +kdb.Cell temp_tc
        +kdb.Cell temp_fc
        +int temp_fc_ind
        +void insert_fill()
    }
    FillOperator : fill_region_multi(region, fill_cell_index, fc_bbox, row_step, column_step, fill_margin, glue_box)
    FillOperator : fill_region(region, fill_cell_index, fc_bbox, row_step, column_step, fill_margin, glue_box)
    note for FillOperator "New attributes and method added to handle temporary layout and cell operations"

File-Level Changes

Change	Details	Files
Introduce temporary layout and cell handling for fill operations	Add temporary layout and cell properties to FillOperator class Create temporary copies of the top cell and fill cell Initialize layout change tracking with start_changes() Modify fill operations to work with temporary cells instead of target cells	`src/kfactory/utils/fill.py`
Add new method to safely transfer fill instances	Add insert_fill method to transfer instances from temporary to target cell Update cell indices during transfer to maintain correct references End layout changes after fill calculation Call insert_fill after fill region calculation is complete	`src/kfactory/utils/fill.py`
Refactor fill_tiled function structure	Move FillOperator instantiation outside of tp.output call Update logging message to be more accurate about the operation stage Remove unnecessary parameters from fill_region_multi call	`src/kfactory/utils/fill.py`

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gdsfactory / kfactory