Restructure the blog for the incoming project archives (#60)

* Upgrade Docusaurus 3.0.1 -> 3.10.2

Needed for the blog work: year-grouped sidebar and blog/tags.yml
descriptions only exist in later 3.x.

Fixes the one swizzle that broke: useSidebarBreadcrumbs/useDocsSidebar
moved from @docusaurus/theme-common/internal to
@docusaurus/plugin-content-docs/client.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit dd63d337c154dbbe9065fa9917f6c0b4ab58192d)

* Restructure the blog for the incoming project archives

Three changes, all aimed at a blog that stays navigable once the
historical Drools/jBPM/OptaPlanner posts land in it:

- Sidebar grouped by year, collapsible. Year grouping is stock 3.10
  behaviour, but upstream renders each year as a plain div; swizzle
  BlogSidebar/Content to wrap them in <details>. Open by default: the
  most recent year, plus the year holding the post being read.

- Tags as sections. blog/tags.yml defines a curated taxonomy — one
  family for components, one for post kinds — each with a description
  that renders on its landing page. onInlineTags/throw makes an
  undeclared tag a build failure, so the set stays curated. Retag the
  four existing posts off the old ad-hoc keywords (apache, 10, kie).

- Excerpt-only post list. None of the posts had a truncation marker, so
  the list rendered every post in full. Add <!-- truncate --> after the
  opening paragraph and drop the H1 that duplicated the frontmatter
  title. onUntruncatedBlogPosts/throw keeps it that way.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit c4cc434bef52e448c38d71a399fa850c3c2d56f7)

* Blog sidebar title: 'All posts', linking to the blog index

Swizzle BlogSidebar/Desktop, where upstream renders the title as a plain
div. With collapsible year groups you can be several years down the list
with no obvious way back, so the heading becomes that way back.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit e6b21703064cb3da7a0b029fd1af368fe383185b)

* Link the blog sidebar to the tags index

Docusaurus has no built-in tag-filter widget, and the blog plugin
registers no global data, so there is no supported way to enumerate tags
from /blog. The native surface is the auto-generated /blog/tags index;
this just makes it reachable from the blog list instead of only from a
post's tag chips.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit 50763e7e8f09d83f8338831be86a2e69f5d3f3c4)

* Sentence case for the remaining headings in the 10.2 editors post

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit bd3f2e1f85746ae23261c741688bbd861ec3d54c)

* Move 'Browse by tag' to the blog's right-hand rail

Swizzle BlogLayout to render the right column unconditionally. Upstream
only renders it when a toc is passed, so /blog had a two-column gap on
the right and nowhere to put the link. Column widths are unchanged — the
rail fills space the grid was already reserving.

Suppressed on the tag pages themselves, where it points at where you
already are, and desktop-only, matching the sidebar and the toc.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit 86226226a87882befae1bb1971e8c664075a363e)

* Address review feedback on the blog restructure

- Year groups: sync open state on client-side navigation. The sidebar
  survives navigation and the groups are keyed by year, so initial state
  alone left the active post hidden inside a collapsed year. The effect
  only ever opens, so a group collapsed by hand stays that way until the
  current post moves into it.
- Tags link: hide it on individual tag pages too, not just the index.
  Keep the link target site-relative — @docusaurus/Link applies baseUrl
  itself, so passing the resolved path would risk prefixing it twice.
- Author link comment: attribute the hover underline to Infima's
  --ifm-link-hover-decoration rather than implying these rules set it.
- Post title: 'Next-generation editors', for consistent sentence case.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>