chore(zarr-indexing): build 0.3.0 changelog (#4445)

* chore(zarr-indexing): render misc fragments and link entries to pull requests

Towncrier's built-in misc type sets showcontent = false, so the package's
misc fragments (#4346, #4364, #4406) would render as bare links. Restate
the five fragment types as zarr-metadata does, with misc showing its
content. Fragments are numbered by the merging PR, so link them under
/pull/ as zarr-metadata does.

Assisted-by: ClaudeCode:claude-opus-5-5

* docs(zarr-indexing): backfill the 0.1.0, 0.2.0 and 0.2.1 release notes

The three releases were tagged without running towncrier, so CHANGELOG.md
stayed empty and their fragments stayed in changes/, where the next build
would have announced them again as new. Build each release from the
fragments its tag shipped: #3906's (renumbered #4196, the PR that merged
it) for 0.1.0, #4222's for 0.2.0, and a new #4252 entry for 0.2.1, whose
only change was the docs build fix. Dates are the tag dates.

Assisted-by: ClaudeCode:claude-opus-5-5

* chore(zarr-indexing): build 0.3.0 changelog

Consume the pending fragments into CHANGELOG.md for the
zarr_indexing-v0.3.0 release.

Minor, not patch: #4350 makes LazyArray indexing lazy by default, so
iterating a view yields views rather than values, and views keep their
literal domain instead of re-zeroing after each selection; #4310 rejects
hand-built diagonal transforms with ValueError.

Assisted-by: ClaudeCode:claude-opus-5-5

* chore(zarr-indexing): date the 0.3.0 release 2026-09-29

Assisted-by: ClaudeCode:claude-opus-5-5

Author: d-v-b