feat: INSTALL.md held to the installation instructions - prerequisites lists generated from the manifest, setup questions checked by docs verify (#154)

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

Files changed:
- CHANGES.md
- INSTALL.md
- VERSION
- instructions/dev/doc-pull-through.md
- instructions/dev/stack-close/SKILL.md
- instructions/setup-instance.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/cli_contract.py
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/install_doc.py
- tools/chemenu/tests/test_install_doc.py

instructions/dev/stack-close/SKILL.md

@@ -105,6 +105,14 @@ and a fresh subagent starts without the session's context).
    behaviour one of these documents describes, update it now; if none did, say so rather than
    leaving the question unasked.
 
+   **If the published diff touches an installation instruction, read the human guide against
+   it once more.** Which instructions those are and which human document answers for each is
+   the pull-through table's row in `instructions/dev/doc-pull-through.md` - `stack-dev` step 5
+   applied it before the publish; this is the second reading, after. A deviation found here is
+   filed as a follow-up issue naming both files and the sentence that disagrees, rather than
+   fixed in this phase: the pull-through before the publish missed it, and that miss is worth a
+   record of its own.
+
    **If that update moved a `##`/`###` heading, the file's table of contents is now stale** -
    regenerate it with `tools/wikitool docs toc --apply`, never by editing the list. The region
    is generated (AGENTS.md invariant 1), `docs verify` fails on stale exactly as on missing, and