track the demo as a real site in examples/, gated like the docs

The human asked for a demo extensive enough to review by hand, tracked as files,
and kept current the way docs are. Generated filler cannot be reviewed — you cannot
read a Go function and see what a reader sees — so the generator is deleted and
`examples/demo-site/` is an ordinary site: 33 Markdown files, six pictures,
site.yaml, a template override and static files.

My reason for generating it was ADR-0011, and I had that rule wrong: it puts the
*author's site root* outside this repository, not fixtures. conventions.md already
keeps golden files in testdata/, and this is the same category one size up. Keeping
both a generator and files would have been two sources of truth, so one had to go.

Kept true by two gates rather than by good intentions. A table-driven test in
internal/web serves the directory through the real handler with one case per
feature — thirty-five of them, each naming what it proves — and verify.sh runs
`khosra check` over it and fails on anything fatal. Adding a feature now means
adding it to the demo and adding its case, and the build says so if you don't.

Extensive on purpose: eleven dated posts so a section actually paginates, a
four-chapter series so first/last are not the neighbours, a gallery with three
JPEGs and an SVG so both the resampled and the untouched paths show, a Bengali-only
bundle, a titleless status, a draft, a future date, an include, a nested extras
tree, and a typography page that demonstrates what the engine will not do.

Two expectations of mine were wrong and the demo corrected them: the site's own
list template overrides *tag* listings too, so there are no group headings there —
which turns out to be the better demonstration of ADR-0046, since the theme picking
the flat shape is exactly the point. And template literal text is not escaped, so
an apostrophe stays an apostrophe.

examples/README.md

@@ -0,0 +1,46 @@
+# examples/
+
+`demo-site/` is a complete khosra site, kept here to be **read and served** — the demonstration a person walks
+through to see what the engine does, and the fixture the engine tests itself against (ADR-0051).
+
+```bash
+make demo                 # serves it at localhost:8080
+khosra check -site examples/demo-site
+```
+
+It is content, not a fixture in disguise: every file is what an author would write. Two things keep it honest,
+both in `verify.sh`:
+
+- `TestTheExampleSiteExercisesEveryFeature` (in `internal/web`) serves this directory through the real handler
+  and asserts one case per feature. A feature that changes shape breaks it.
+- `khosra check` runs over it and must report nothing fatal.
+
+**Adding a feature means adding it here**, with a case in that test. A feature the example does not show is a
+feature nobody can see working, and the gates are what stop that from being optional.
+
+## What each part is for
+
+| Path | Demonstrates |
+|---|---|
+| `site.yaml` | the two site-level settings: `base` and `title` |
+| `content/posts/day-01…11` | pagination — eleven dated posts against a page size of ten |
+| `content/posts/first-light/` | two languages, a directory bundle owning a picture, a figure with a caption |
+| `content/posts/only-english` | the fallback chain, and a canonical link naming the variant actually served |
+| `content/posts/renamed-thing/` | `slug` moving an address, `aliases` keeping the old one working |
+| `content/posts/unfinished` | a draft: invisible without `-dev on` |
+| `content/posts/scheduled` | a future date: published by the clock, with nothing to run |
+| `content/comics/the-long-monsoon/` | a series — structural membership, sparse `order`, prev/next/first/last, an archive, and a landing page in two languages |
+| `content/art/monsoon-studies/` | a gallery: three JPEGs sized into a `srcset`, and an SVG left exactly as drawn |
+| `content/writing/notes-on-water/` | an include whose fragment has no URL, and an `extras/` tree with a nested directory |
+| `content/writing/typography` | what the engine does to prose, and what it deliberately does not |
+| `content/pages/*` | undated bundles: reachable, and absent from every feed |
+| `content/pages/bengali-only` | a bundle that exists in one non-default language only |
+| `content/status/*` | a titleless bundle — legal, and the one `check` warning this site expects |
+| `templates/list.html` | overriding a single named block and inheriting the document |
+| `static/note.txt` | files served verbatim |
+
+## The one expected warning
+
+`khosra check` reports the titleless status note. That is deliberate: titleless is legal, the theme falls back
+to the bundle's key, and the warning exists so an author who did not mean it finds out. A *fatal* finding here
+would fail `verify.sh`.