feat: INSTALL.md is the English installation tutorial; new tutorial docs/tutorials/first-source-to-first-answer.md with a shipped sample source; README.md links it as its first-ingestion step (#191)

Files changed:
- CHANGES.md
- INSTALL.md
- README.md
- VERSION
- docs/reference/commands/types-instructions-and-docs.md
- docs/tutorials/README.md
- docs/tutorials/first-source-to-first-answer.md
- docs/tutorials/sample-source.md
- instructions/dev/doc-pull-through.md
- tools/CONTRACT.md
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/install_doc.py
- tools/chemenu/tests/test_install_doc.py

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

instructions/dev/doc-pull-through.md

@@ -41,7 +41,7 @@ touched; a row that does not apply needs no action.
    | A task-tracker adapter (`tools/chemenu/tasks/`), its recorded fixtures, or the live suite | [instructions/dev/tracker-testing.md](tracker-testing.md), and `MANIFEST.json` beside the fixtures when they were re-recorded |
    | A skill's own step sequence or catalogue | The skill's `SKILL.md` source under `instructions/<name>/` or `instructions/dev/<name>/`; for a shipped skill (not under `instructions/dev/`) whose name or `description` changed, or one added or removed, `wikitool docs reference --apply` for the skill catalogue `docs/reference/skills.md` |
    | A per-checkout configuration file an instance owns (`.wikitool-tasks.json`, `.wikitool-telemetry.json`, `.wikitool-remotes.json`, `.wikitool-upload.json`) | [docs/reference/configuration.md](../../docs/reference/configuration.md), where an operator looks the shape up - written by hand, since nothing generates it; the [setup-instance.md](../setup-instance.md) decision point that offers it during setup; and `doctor`'s own row in [tools/CONTRACT.md](../../tools/CONTRACT.md), since `doctor` is what reports the file's state |
-   | An installation instruction - [preflight.md](../preflight.md), [setup-instance.md](../setup-instance.md), [bootstrap.md](../bootstrap.md), [upgrade-instance.md](../upgrade-instance.md) - or `tools/prerequisites.txt` | [INSTALL.md](../../INSTALL.md), the human guide to the same procedure - for `upgrade-instance.md`, [docs/how-to/update-an-instance.md](../../docs/how-to/update-an-instance.md) instead. Read it against the instruction: what to prepare, the sentence for the agent, what the agent asks, where it stops and why. `docs verify` checks only the two enumerable overlaps - the prerequisites lists, which `wikitool docs prerequisites --apply` regenerates from the manifest, and the setup questions: a question the agent asks the user carries `<!-- setup-question: <key> -->` where it is asked in `setup-instance.md`, and `INSTALL.md` § "Was der Agent dich fragt" names it with the same marker. Every other sentence is this session's to compare. `INSTALL.md` does not retell the steps, so a change to their order or wording alone moves nothing there |
+   | An installation instruction - [preflight.md](../preflight.md), [setup-instance.md](../setup-instance.md), [bootstrap.md](../bootstrap.md), [upgrade-instance.md](../upgrade-instance.md) - or `tools/prerequisites.txt` | [INSTALL.md](../../INSTALL.md), the human guide to the same procedure - for `upgrade-instance.md`, [docs/how-to/update-an-instance.md](../../docs/how-to/update-an-instance.md) instead. Read it against the instruction: what to prepare, the sentence for the agent, what the agent asks, where it stops and why. `docs verify` checks only the two enumerable overlaps - the prerequisites lists, which `wikitool docs prerequisites --apply` regenerates from the manifest, and the setup questions: a question the agent asks the user carries `<!-- setup-question: <key> -->` where it is asked in `setup-instance.md`, and `INSTALL.md` § "What the agent asks you" names it with the same marker. Every other sentence is this session's to compare. `INSTALL.md` does not retell the steps, so a change to their order or wording alone moves nothing there |
    | [dev-setup.md](dev-setup.md), the release workflow (`version bump`/`version release`/`publish`/CI), or another developer-facing process | [docs/dev/development.md](../../docs/dev/development.md), read against it the same way - nothing checks this pair at all. A page under `docs/dev/` is never shipped, so it may link into `instructions/dev/` and cite issue numbers |
    | A new page type the stack requires, or a new collection | Its type-spec and `COLLECTION.md` (both as the `.template` an instance adopts), the collection table in [kb/CONTRACT.md](../../kb/CONTRACT.md), and **both adoption paths**: [setup-instance.md](../setup-instance.md) for a fresh instance and [upgrade-instance.md](../upgrade-instance.md) for an existing one, where an unadopted template is what `docs verify` refuses. A new or changed `root: kb` type-spec or its schema - description, `layout:`, subtype enum, required fields - also needs `wikitool docs reference --apply` for `docs/reference/page-types.md` |