…mode

Fixes two confirmed bugs from a manual site audit:

1. 12 broken links (404s), traced to two root causes:
   - 7 nav/footer links pointed to trailing-slash directory URLs
     (/blog/, /solutions/, /docs/, /questions/, /compare/, /examples/,
     /use-cases/) but the site's build.format:'file' + trailingSlash:
     'never' config emits flat *.html files, not dir/index.html. Every
     such link across the whole site (crumbs, sidebar, cards) has been
     corrected to the *.html form the build actually produces, and new
     landing pages were added for each of these sections (blog, compare,
     docs, questions, solutions, docs/guides) built from the real
     existing content in each folder, not fabricated pages.
   - 2 dead links to /docs/guides/capability-authoring.html and
     /docs/guides/workflow-authoring.html, referenced from the docs
     sidebar and several content pages, pointing to guides that were
     never built. Redirected to real existing content that already
     covers the same material (quickstart.html, concepts.html#workflows)
     rather than inventing new guide pages.
   - /examples/ and /use-cases/ had no page at all. Built both from
     content that already exists elsewhere on the site (the capability
     contract example used on the homepage/docs, and the use-case
     descriptions already on solutions pages) rather than fabricating
     new claims.

2. The docs sidebar was hardcoded HTML duplicated across all 5 docs
   pages, and had drifted into three different structures (quickstart
   and concepts each had a unique variant; architecture, cli-reference,
   and troubleshooting shared a third, the one with the dead guide
   links). Extracted to a single DocsSidebar.astro component with an
   `active` prop, used consistently by all 5 pages plus the two new
   docs index pages.

3. Nav contrast bug in light mode: the homepage hero has a hardcoded-
   dark background regardless of theme (brand art), but the nav's
   transparent (unscrolled) state used theme-aware --fg/--fg-muted,
   which flips to near-black in light mode — rendering the wordmark,
   nav links, and GitHub button nearly invisible against the dark hero.
   Scoped a fix to body.home only (verified no other page has a
   hardcoded-dark hero) forcing light nav text while transparent,
   falling back to normal theme-aware color once scrolled/solid.

Verified: 0 broken internal links across all 88 built pages (up from
80 — 8 new landing/index pages), 0 canonical URLs with a trailing
slash, docs sidebar renders identically (same links, correct active
state) across all 5 docs pages plus computed styles confirming legible
nav text in light mode on the homepage.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>