feat: export guidelines - the guideline pages as a generated GUIDELINES.md, pushed into the captured repositories behind the Guideline Push Gate (#179)

Files changed:
- AGENTS.md
- CHANGES.md
- README.md
- VERSION
- docs/why-gates-are-code.md
- instructions/gates.md
- instructions/kb-profiles.md
- kb/CONTRACT.md
- kb/CONVENTIONS.md
- kb/CONVENTIONS.md.template
- raw/CONTRACT.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/cli.py
- tools/chemenu/cli_contract.py
- tools/chemenu/commands/export_cmd.py
- tools/chemenu/commands/page_ops.py
- tools/chemenu/commands/raw_cmd.py
- tools/chemenu/commands/search.py
- tools/chemenu/guideline_export.py
- tools/chemenu/kb_scan.py
- tools/chemenu/repo_capture.py
- tools/chemenu/search/filters.py
- tools/chemenu/tests/test_cli.py
- tools/chemenu/tests/test_export_guidelines.py

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

kb/CONTRACT.md

@@ -13,7 +13,7 @@ how it works, so it is identical everywhere and `dist export` ships it verbatim.
 
 **What an instance decides for itself is next door, in
 [kb/CONVENTIONS.md](CONVENTIONS.md)** - the language pages are written in, the headings its two
-generated regions render under, the naming forms, the tone, the hedging rule. That file binds exactly as this one does; it is simply owned by the instance
+generated regions render under, the naming forms, the tone, the hedging rule, which pages leave the wiki as guidelines. That file binds exactly as this one does; it is simply owned by the instance
 rather than by the stack, so the distribution ships only its `.template` and the instance writes
 the real one. Read both, plus the target collection's `kb/<name>/COLLECTION.md` (also
 instance-owned), before writing or editing a page.
@@ -40,6 +40,7 @@ looks like) are in neither - they belong to the type-specs and are printed by
   - [Generated regions](#generated-regions)
 - [Linking](#linking)
 - [Provenance and citation](#provenance-and-citation)
+- [Pages that leave the wiki: guidelines](#pages-that-leave-the-wiki-guidelines)
 - [What does not belong here](#what-does-not-belong-here)
 <!-- /wikitool:toc -->
 
@@ -329,6 +330,23 @@ Every claim is either traceable to a raw file or explicitly marked as not.
 If no raw file or existing page backs an answer, say so explicitly rather than synthesizing
 one - and never file the synthesized version back into the wiki.
 
+## Pages that leave the wiki: guidelines
+
+`tools/wikitool export guidelines` renders a selection of pages into one generated
+`GUIDELINES.md` and, behind the Guideline Push Gate, writes it into the captured repositories that
+opted in ([raw/CONTRACT.md](../raw/CONTRACT.md#getting-a-repository-in-raw-capture)). Which pages
+that is, is not decided here: the stack defines no type and no field for a guideline, and the
+selection - a set of `search` predicates - is written down in
+[kb/CONVENTIONS.md](CONVENTIONS.md) by the instance.
+
+What the stack does decide is how a page reads once it has left. The export is mechanical:
+frontmatter, the generated links and footnotes regions and every citation marker are dropped,
+`[[Title|Text]]` becomes `Text` and `[[Title]]` becomes `Title`, and code is left untouched. So a
+guideline has to stand on its own in another repository - without its links to follow and without
+the sources behind it - and an edit to one reaches every target repository on the next export.
+The file there is never edited by hand: the next export overwrites it, so a correction goes into
+the page.
+
 ## What does not belong here
 
 - Raw source material - it stays immutable under `raw/`.