Merge branch 'feat/p3-python-remote-edit' into feat/p3-wasm-swmr-python

# Conflicts:
#	CHANGELOG.md
#	docs/design/range-reads.md
#	docs/known-issues.md

docs/known-issues.md

@@ -30,6 +30,33 @@ h5py's SWMR reader). A file still being written is read with
 `File::open_swmr` (see `docs/design/swmr.md`); `File::open` maps the file
 at its length at open and is not meant for files that change while open.
 
+## Shrinking a chunked dataset with no recorded maximum scrambled it
+
+**Status:** fixed 2026-09-27, before any release (`FileEditor::resize`
+shipped on main in PR #18, a4c2ace). Files the writer produced before the
+fix still lack the maximum; see *Existing files*.
+
+clawhdf5's writer stored no maximum dimensions for a chunked dataset
+created without a `maxshape` (libhdf5 always stores one, equal to the
+dimensions when none is given). With none recorded, the maximum is the
+current dimensions (`H5S_extent_get_dims`), and a Fixed Array chunk index
+places chunks by the maximum. `FileEditor::resize` changed only the
+current dimensions, so a shrink moved every existing chunk and every
+reader returned wrong values; after a shrink the dataset could not grow
+back. Found by the review of the Python editing work.
+
+**Fix:** before the first resize of such a dataset the editor records the
+maximum libhdf5 would have written (the dimensions the index was built
+with); the writer now records it for every chunked dataset. **Test:**
+`crates/clawhdf5/tests/edit_resize_interop.rs`. **Existing files:**
+datasets written before the fix have no recorded maximum. The fixed
+editor handles them; **libhdf5 (h5py `Dataset.resize`, `H5Dset_extent`)
+does not** — it scrambles them the same way, and lets them grow past
+their Fixed Array. Resize them once with a fixed `FileEditor` (a resize
+to the same shape changes nothing; shrink and grow back) before letting
+libhdf5 resize them. A dataset already shrunk by the unfixed
+editor holds misplaced chunks; rewrite it from a good copy.
+
 ## Fletcher-32 checksums disagreed with libhdf5 on about 1 chunk in 32768
 
 **Status:** fixed 2026-09-26, after v2.7.0. **Every release (v2.1.0 to
@@ -139,6 +166,57 @@ space it leaves is too small for its next, larger version.
 **No journal.** A crash while an edit patches existing structures can leave
 the file inconsistent; see the `FileEditor` documentation.
 
+**Renamed files outside Linux.** Edits always go to the file the editor
+opened. `FileEditor::reader()` (which the Python `'r+'` handle reads
+through) reopens it through `/proc/self/fd` on Linux; elsewhere it reopens
+the path, and after the path was renamed or replaced it fails (on Unix;
+Windows cannot tell and would read whatever the path names).
+
+## Python in-place editing (`clawhdf5.File(path, 'r+')`) limits
+
+**Status:** open (added 2026-09-27). The Python bindings edit through
+`FileEditor`, so its limits above apply, raised as `NotImplementedError`
+before anything is written. On top of them:
+
+- **No new or deleted objects:** `create_dataset`/`create_group` in an
+  `'r+'` file, `del f[name]` and `del obj.attrs[name]` raise
+  `NotImplementedError` (the editor changes values, shapes and
+  attributes only). Mode `'a'` works on an existing file only.
+- **Not writable from Python:** compound fields by name (`ds['x'] = …`;
+  whole elements of the same structured dtype are), HDF5 array-type
+  elements, variable-length data, strings padded with spaces or
+  NUL-terminated (libhdf5 converts those differently from numpy; NUL-padded
+  ones, h5py's, are writable), compounds containing such strings, null
+  dataspaces, index-list writes of more than 2²² elements (write them
+  in slices), and boolean-mask keys (`ds[mask] = v`, and mask reads;
+  h5py supports both).
+- **`str` attributes are fixed-length UTF-8**, where h5py writes
+  variable-length strings: h5py reads them back as `bytes`
+  (`numpy.bytes_`), not `str`.
+- **Numeric conversion follows libhdf5's native-order results, not its
+  bugs.** Arrays are converted as libhdf5 converts them (integers
+  saturate, floats are truncated toward zero and clipped), checked value by
+  value against h5py 3.16 / HDF5 2.0 in
+  `crates/clawhdf5-py/tests/test_edit.py::test_numeric_conversions_match_h5py`
+  (2026-09-27, tank). Where libhdf5 itself is inconsistent, clawhdf5
+  differs from h5py on purpose:
+  - NaN into an integer dataset is a `ValueError` (libhdf5 stores 0, the
+    minimum or 2⁶³ depending on the type);
+  - when the dataset or the array is not in native byte order, libhdf5's
+    "soft" conversions store a float in (-1, 0) as the integer minimum and
+    wrap an unsigned value too large for the signed type of the same size
+    (65535 → -1); clawhdf5 gives 0 and the maximum, as libhdf5 does in
+    native order;
+  - libhdf5's native casts that are undefined in C: half floats into
+    unsigned integers (-1 → 65535, +inf → 0), half-float ±inf into signed
+    integers (→ minimum), a float equal to the integer maximum rounded up
+    in its precision (`float32(2**31 - 1)` into `int32`, `float64(2**64 -
+    1)` into `uint64`: → minimum or 0); clawhdf5 saturates;
+  - a double in (65504, 65520) into a half float: libhdf5 stores infinity,
+    clawhdf5 (numpy) rounds to 65504 as IEEE 754 does.
+- **Each edit reopens the file** (a new memory map) so that reads see it;
+  reads from other threads wait while an edit is written.
+
 ## Selection reads that decode more than the selection
 
 **Status:** open (documented 2026-09-26). `Dataset::read_selection` (and so
@@ -867,9 +945,9 @@ cache, but:
   `read_*_zerocopy`) need the file in memory and answer
   `FormatError::ContiguousStorageRequired` otherwise; `File::as_bytes()`
   panics for such a file (`File::contiguous_bytes()` is the fallible form).
-  `LazyFile`, `MmapFile` and the Python and wasm bindings still read a
-  whole file (`h5rs` reads through `File::storage`, and takes URLs with its
-  `remote` feature).
+  `LazyFile`, `MmapFile` and the wasm bindings still read a whole file
+  (`h5rs` and the Python bindings read through `File::storage`, and take
+  URLs: `h5rs` with its `remote` feature, Python with `clawhdf5.File(url)`).
 - The file's length is read once, at open: a growing file (SWMR) is not
   followed (milestone M5). A remote file is pinned at open, so one that
   grows is `RemoteError::FileChanged`.
@@ -885,9 +963,12 @@ cache, but:
 **Status:** open (added 2026-09-26, milestone M3 of
 `docs/design/range-reads.md`).
 
-- **Python and the browser cannot open URLs yet.** `clawhdf5.File` (PyO3)
-  parses through `File::as_bytes`, which a remote file does not have; the
-  wasm reader's `openUrl` is milestone M4.
+- **The browser cannot open URLs yet**: the wasm reader's `openUrl` is
+  milestone M4. Python can (`clawhdf5.File(url)`, since 2026-09-27), but
+  the default wheel reads plain `http://` only: `https://` needs a wheel
+  built with `--features https` (rustls with ring, which compiles C), and
+  `s3://`, `gs://`, `az://` the `s3`, `gcs`, `azure` features (aws-lc-rs).
+  The Python tests run against an in-process `http.server` only.
 - **The block size is fixed** (1 MiB unless `CacheConfig` says otherwise).
   The design's policy of using a paged file's page size as the block size
   is not implemented, and only the first block is read ahead.