docs: fix lists swallowed into the preceding paragraph

[dimitri-yatsenko]

Reported: the "Addressing schemes" bullet list on https://docs.datajoint.com/reference/specs/codec-api/ is broken.

Root cause

A Markdown list needs a blank line after a paragraph lead-in. Without one, this:

**Addressing schemes:**
- **Hash-addressed**: Path from content hash. Automatic deduplication.
- **Schema-addressed**: Path mirrors database structure. One location per entity.

renders as a single run-on <p> with literal dashes:

<p><strong>Addressing schemes:</strong>
- <strong>Hash-addressed</strong>: Path from content hash. Automatic deduplication.
- <strong>Schema-addressed</strong>: Path mirrors database structure. One location per entity.</p>

Neither mkdocs build nor the existing checks warn about this, so the pages just quietly looked wrong.

Scope

Not one page. A sweep of the built output found 149 occurrences across 23 files, all the same shape — a bold lead-in (Characteristics:, Common causes:, Rules:, Best for:) followed immediately by list items:

file	count
how-to/choose-storage-type.md	30
reference/errors.md	16
reference/specs/query-algebra.md	11
reference/specs/autopopulate.md	9
reference/specs/data-manipulation.md	9
reference/specs/object-store-configuration.md	8
reference/specs/type-system.md	8
how-to/migrate-to-v20.md	8
reference/specs/job-metadata.md	7
reference/specs/npy-codec.md	7
reference/specs/table-declaration.md	5
how-to/use-npy-codec.md	5
how-to/use-plugin-codecs.md	5
reference/specs/codec-api.md	4
reference/specs/master-part.md	4
(8 more with 1–3 each)	11

Guard against recurrence

scripts/check_markdown_lists.py + a Markdown Lint workflow. This is detectable in source without a build, so the job is just a checkout and one script. It takes --fix to apply the spacing.

Only top-level lists directly under an ordinary paragraph are reported. Lists already inside a list block — including ones whose previous line is a wrapped continuation of an earlier item — are left alone, so tight lists stay tight. (My first pass got this wrong and made 10 existing items loose; the state tracking now prevents that.)

Verification

Built before and after with --strict, comparing content-area lists only:

	swallowed	<li>	loose items
before	149	2377	71
after	0	2870	71
delta	−149	+493	+0

493 list items recovered, no tight list turned loose, --strict passes. The checker run against the pre-fix codec-api.md flags all 4 of its sites including line 529, the reported one.

Note for review

The 149 changes are mechanical (blank-line insertion only, no prose touched), so the diff is best read with whitespace shown. One content gap I did not touch: the codec-api addressing-schemes list documents only Hash and Schema, but the table directly above it also has a Reference scheme for <filepath@>. Adding that line is a content decision, so I left it.