* main:
  Revise (pydata#9366)
  Fix rechunking to a frequency with empty bins. (pydata#9364)
  whats-new entry for dropping python 3.9 (pydata#9359)
  drop support for `python=3.9` (pydata#8937)
  Revise (pydata#9357)
  try to fix scheduled hypothesis test (pydata#9358)

* main:
  Improve error message for missing coordinate index (pydata#9370)
  Add flaky to TestNetCDF4ViaDaskData (pydata#9373)
  Make chunk manager an option in `set_options` (pydata#9362)
  Revise (pydata#9371)
  Remove duplicate word from docs (pydata#9367)
  Adding open_groups to BackendEntryPointEngine, NetCDF4BackendEntrypoint, and H5netcdfBackendEntrypoint (pydata#9243)

* main:
  Adds copy parameter to __array__ for numpy 2.0 (pydata#9393)
  `numpy 2` compatibility in the `pydap` backend (pydata#9391)
  pyarrow dependency added to doc environment (pydata#9394)
  Extend padding functionalities (pydata#9353)
  refactor GroupBy internals (pydata#9389)
  Combine `UnsignedIntegerCoder` and `CFMaskCoder` (pydata#9274)
  passing missing parameters to ZarrStore.open_store when opening a datatree (pydata#9377)
  Fix tests on big-endian systems (pydata#9380)
  Improve error message on `ds['x', 'y']` (pydata#9375)

* main:
  Accessibility: Add keyboard handling for XArray HTML view (pydata#9412)
  [pre-commit.ci] pre-commit autoupdate (pydata#9316)
  [skip-ci] Speed up docs build by limiting toctrees (pydata#9395)
  fix the failing `pre-commit.ci` runs (pydata#9411)
  Update benchmarks.yml (pydata#9406)
  GroupBy(multiple groupers) (pydata#9372)
  Encode/decode property tests use variables() (pydata#9401)

This reverts commit 7a99c8f.

* main: (29 commits)
  Release notes for v2024.09.0 (pydata#9480)
  Fix `DataTree.coords.__setitem__` by adding `DataTreeCoordinates` class (pydata#9451)
  Rename DataTree's "ds" and "data" to "dataset" (pydata#9476)
  Update DataTree repr to indicate inheritance (pydata#9470)
  Bump pypa/gh-action-pypi-publish in the actions group (pydata#9460)
  Repo checker (pydata#9450)
  Add days_in_year and decimal_year to dt accessor (pydata#9105)
  remove parent argument from DataTree.__init__ (pydata#9465)
  Fix inheritance in DataTree.copy() (pydata#9457)
  Implement `DataTree.__delitem__` (pydata#9453)
  Add ASV for datatree.from_dict (pydata#9459)
  Make the first argument in DataTree.from_dict positional only (pydata#9446)
  Fix typos across the code, doc and comments (pydata#9443)
  DataTree should not be "Generic" (pydata#9445)
  Disallow passing a DataArray as data into the DataTree constructor (pydata#9444)
  Support additional dtypes in `resample` (pydata#9413)
  Shallow copy parent and children in DataTree constructor (pydata#9297)
  Bump minimum versions for dependencies (pydata#9434)
  Always include at least one category in random test data (pydata#9436)
  Avoid deep-copy when constructing groupby codes (pydata#9429)
  ...

* main:
  Opt out of floor division for float dtype time encoding (pydata#9497)
  fixed formatting for whats-new (pydata#9493)
  Forbid modifying names of DataTree objects with parents (pydata#9494)
  DAS-2155 - Merge datatree documentation into main docs. (pydata#9033)
  Make illegal path-like variable names when constructing a DataTree from a Dataset (pydata#9378)
  Ensure TreeNode doesn't copy in-place (pydata#9482)
  `open_groups` for zarr backends (pydata#9469)
  Update pyproject.toml (pydata#9484)
  New whatsnew section (pydata#9483)

* main:
  Turn off survey banner (pydata#9512)
  Stateful test: silence DeprecationWarning from drop_dims (pydata#9508)

* main: (85 commits)
  Refactor out utility functions from to_zarr (pydata#9695)
  Use the same function to floatize coords in polyfit and polyval (pydata#9691)
  Add `DataTree.persist` (pydata#9682)
  Typing annotations for arithmetic overrides (e.g., DataArray + Dataset) (pydata#9688)
  Raise `ValueError` for unmatching chunks length in `DataArray.chunk()` (pydata#9689)
  Fix inadvertent deep-copying of child data in DataTree (pydata#9684)
  new blank whatsnew (pydata#9679)
  v2024.10.0 release summary (pydata#9678)
  drop the length from `numpy`'s fixed-width string dtypes (pydata#9586)
  fixing behaviour for group parameter in `open_datatree` (pydata#9666)
  Use zarr v3 dimension_names (pydata#9669)
  fix(zarr): use inplace array.resize for zarr 2 and 3 (pydata#9673)
  implement `dask` methods on `DataTree` (pydata#9670)
  support `chunks` in `open_groups` and `open_datatree` (pydata#9660)
  Compatibility for zarr-python 3.x (pydata#9552)
  Update to_dataframe doc to match current behavior (pydata#9662)
  Reduce graph size through writing indexes directly into graph for ``map_blocks`` (pydata#9658)
  Add close() method to DataTree and use it to clean-up open files in tests (pydata#9651)
  Change URL for pydap test (pydata#9655)
  Fix multiple grouping with missing groups (pydata#9650)
  ...

* main:
  update mypy to 1.13 (pydata#9687)