feat(docs): publish the context/ prose as a site folded into Pages

The landing page is the site root and the app is /app/; the prose now sits
at /docs/, assembled by the same web/assemble.sh the Pages job and the
browser harness both run, so what ships and what is tested are one tree.

Published: design-notes, design-principles, repo-map, the three ADRs, the
seven context/code/ arguments, and the 501 test-evidence entries as their
own clearly-labelled section. Not published: context/plan.md, which is an
agent prompt about a launch rather than a description of the program, and
context/cloud-agents.md, which is addressed to nobody who visits a website.
Neither is referenced by a published document outside a code fence, so
leaving them out dangles nothing. The reasoning is context/code/doc-site.md,
which is itself published.

Two things the corpus needed that a generator would not have given it. The
~190 improvise-xxxx citations resolve to a generated ticket index built from
the already-public .beads/issues.jsonl rather than to an invented URL that
would 404; an id the export does not yet carry stays plain text. And a code
span that is wholly a repo path links to GitHub at the assembled ref, but
only when the file exists on disk, so a stale citation degrades to text.

The generator link-checks its own output and exits non-zero on a break, and
assemble.sh runs under set -eu, so a dead cross-reference fails the assembly
rather than shipping. It earned that on its first two runs: it caught a
fence-close regex comparing a three-character marker to a one-character
string, which swallowed every document from its first code block onward, and
a list parser that ended the gotcha list at the first blank line, emitting 1
of the 48 anchors the jump strip links to. Proved by injection afterwards --
renaming the anchors reports 48 missing anchors, pointing the ticket links at
an ungenerated page reports 763 missing pages.

No framework, no node_modules for the site, no build step beyond one
zero-dependency node script, matching the landing page's posture.

improvise-djoo

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

.github/workflows/ci.yml

@@ -228,6 +228,12 @@ jobs:
       - name: Build the wasm bundle
         run: ./web/build.sh
 
+      # assemble.sh generates the prose site with node. The runner image ships
+      # one, but pinning it here is what makes a local run evidence about this.
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "24"
+
       # `web/assemble.sh`, not an inline copy of it: the browser harness job
       # below assembles the same tree, and a harness that runs against a
       # different arrangement of files is testing something nobody deploys.