docs(readme): link the essay, the compare page, the when-to-use page and the deck (#22955)

Fixes #22952
Clause-②: no

Three additions to `README.md`; no other file, and nothing else in the
file. Diff: 8 insertions, 1 deletion. The one modified line is the "Read
why" line: its text stays the same and it gets a second link.

## What changed

1. **Entry line under the demo.** Inside the centred block that holds
the GIF, after the "Watch: ObjectStack in 90 Seconds" line: a line
break, then one more `sub` line. It holds three links separated by the
caption's own ` · `: "Why it exists" (the essay), "How it
compares" (the compare page) and "When to use it" (the when-to-use
page).
2. **Two pointer sentences closing "What we mean by ontology".** They go
in a new paragraph after the existing one, which is byte-identical. "How
it compares" sets ObjectStack beside knowledge ontologies, semantic
layers, operational ontologies, metadata platforms, and AI code
generation. "When to use it" says where it fits today and where it does
not. Both sentences restate the target pages' own frontmatter
descriptions, with no new claim, number or superlative.
3. **The deck beside "Read why".** In the "You own it" quote block, the
same line now reads "Read why · the talk as a deck (PDF)", and the
second link goes to the PDF.

All four destinations are absolute URLs, like the README's other site
links:

- https://objectstack.ai/blog/the-ontology-is-the-software
- https://objectstack.ai/docs/concepts/compare
- https://objectstack.ai/docs/concepts/when-to-use
- https://objectstack.ai/decks/the-ontology-is-the-software.pdf

## The targets exist on main

Measured at base `51b43a8d`:

- `content/docs/concepts/compare.mdx` and
`content/docs/concepts/when-to-use.mdx` are present (`git cat-file -e`).
The docs-site resolver that `check:published-readme-links` uses
(`pageCandidates` from `scripts/check-docs-redirects.mjs`) maps
`/docs/concepts/compare` and `/docs/concepts/when-to-use` to those two
files. The negative control `/docs/concepts/no-such-page-control` maps
to no page. Both pages are listed in `content/docs/concepts/meta.json`.
- `content/blog/the-ontology-is-the-software.mdx` is present, and the
README already linked its URL ("Read why").
- `apps/docs/public/decks/the-ontology-is-the-software.pdf` is present,
and the essay already links the same absolute URL.

GitHub's own rendering of the branch README carries the new anchors. The
read was `GET /repos/objectstack-ai/objectstack/readme` at this branch
with the html media type, so the sanitizer is included. Anchor counts:
compare 2, when-to-use 2, essay 2 (the existing "Read why" plus the new
entry line), deck 1. The `sub` line renders with its three links.
Control: the same read against `main` carries 0 compare anchors.

## Gates

`node scripts/pm/dispatch-gates.mjs --commands --repo
objectstack-ai/objectstack` derived 9 gates from the merge base (1 path:
`README.md`). Every one ran at `6fec6e55`, with the exit code captured
before any pipe:

| command | exit | gate's own verdict |
|---|---|---|
| `node scripts/check-closing-keyword-parity.mjs` | 0 | OK (3 parsers
agree on all 9 keywords) |
| `node scripts/check-closing-keyword-parity.mjs --self-test` | 0 | 40
assertions, 5 mutations driven to red |
| `node scripts/check-comment-mask-corpus.mjs` | 0 | 8819 files, 0
disagree, 0 unparseable |
| `pnpm check:doc-anchors` | 0 | 484 internal fragment links all resolve
|
| `pnpm check:driver-memory-census` | 0 | OK |
| `pnpm check:gitlink-declared` | 0 | OK, 0 gitlinks |
| `pnpm check:nul-bytes` | 0 | OK, no raw ASCII control bytes |
| `pnpm check:refd-timer-probe` | 0 | OK |
| `pnpm check:watch-hint-literal` | 0 | 72 declarations, all admitted |
| `pnpm check:published-readme-links` | 0 | 226 links across 102
published markdown files; 144/144 relative targets found |

`dispatch-gates --ran` reconciliation: 9 derived, 9 run, 0 NOT-MEASURED,
0 UNRUN. This is a derived zero: all 9 recorded an exit code.
`check:published-readme-links` is outside the derivation and was run
because the dispatch named it. See the first acceptance note for what
its green covers.

No build or test: the diff touches no package.

## Acceptance notes

- **`check:published-readme-links` green tells us nothing about this
diff.** The root `README.md` is not among the 102 published markdown
files the gate reads: the root package is private, and no package ships
the root README. The gate does resolve absolute `objectstack.ai/docs`
URLs against `content/docs`, but only inside that population. That is
why the resolver measurement above was taken directly. The card's
"leaves absolute URLs alone" holds for the network (the gate never
requests a URL), not for docs-site resolution.
- **Nothing in CI resolves the root README's absolute docs-site links.**
The `check-links.yml` lychee lane globs `README.md` but runs
`--offline`, which leaves absolute URLs out as well. If the compare page
or the when-to-use page were renamed, these links would point at a 404
with every gate green. This is an observation, not a current defect, so
it is not filed. Carrier: none.
- **No other open PR touches `README.md`.** All 18 open PRs were read
file by file at the time of writing, and none touches it. The three
`copilot/update-readme-*` heads on origin belong to PRs that are closed
and merged; none is open.
- **Changeset: none.** `packages/**` is untouched, and the README ships
in no published package. Labelled `skip-changeset`.
- **Not in this PR:** repository topics and the About line
(settings-page values, the maintainer's clicks), the home page and the
blog figures (separate cards).

---
_Generated by [Claude
Code](https://claude.ai/code/session_011hRnra93sK5Q2gTYYTbdJR)_

Co-authored-by: Claude <noreply@anthropic.com>

Author: objectstack-fleet[bot]

README.md

@@ -21,6 +21,8 @@
   <sub><b>1</b> · One definition, and the app runs &nbsp;·&nbsp; <b>2</b> · An agent creates a record over MCP &nbsp;·&nbsp; <b>3</b> · A read-only identity is refused</sub>
   <br>
   <a href="https://youtu.be/CX_FlOoOtr0"><b>▶&nbsp; Watch: ObjectStack in 90 Seconds</b></a>
+  <br>
+  <sub><a href="https://objectstack.ai/blog/the-ontology-is-the-software">Why it exists</a> &nbsp;·&nbsp; <a href="https://objectstack.ai/docs/concepts/compare">How it compares</a> &nbsp;·&nbsp; <a href="https://objectstack.ai/docs/concepts/when-to-use">When to use it</a></sub>
 </p>
 
 You build & ask with Claude Code or any coding agent: the agent writes the
@@ -88,6 +90,11 @@ runtime, as hooks, action bodies, CEL, and constrained JSX. The full account is
 [Business Ontology](https://objectstack.ai/docs/concepts/ontology); the short
 form is the [glossary entry](https://objectstack.ai/docs/getting-started/glossary#business-ontology).
 
+[How it compares](https://objectstack.ai/docs/concepts/compare) sets ObjectStack
+beside knowledge ontologies, semantic layers, operational ontologies, metadata
+platforms, and AI code generation. [When to use it](https://objectstack.ai/docs/concepts/when-to-use)
+says where it fits today and where it does not.
+
 ## The runtime runs it
 
 Point an agent at an empty repo and you get a one-off codebase: every screen
@@ -207,7 +214,7 @@ graph held inside a vendor's system.
 > The ontology is the software. Your objects, relations, actions, permissions,
 > flows, and agent and tool definitions are your business ontology — and the
 > definition layer of the AI era should be an open protocol you own.
-> [Read why](https://objectstack.ai/blog/the-ontology-is-the-software).
+> [Read why](https://objectstack.ai/blog/the-ontology-is-the-software) · [the talk as a deck (PDF)](https://objectstack.ai/decks/the-ontology-is-the-software.pdf).
 
 ## Ship it