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/CONVENTIONS.md.template

@@ -34,6 +34,7 @@ marker pair, so a rename re-renders words and nothing else.
 - [Tone](#tone)
 - [Relationship labels](#relationship-labels)
 - [Hedging](#hedging)
+- [Guidelines for other repositories](#guidelines-for-other-repositories)
 - [Keeping this file honest](#keeping-this-file-honest)
 <!-- /wikitool:toc -->
 
@@ -112,6 +113,16 @@ sourced claim, in the KB language.}
 (`raw/CONTRACT.md`'s `authority` axis) from one resting on `opinion`, and how it signals
 disagreement between sources.}
 
+## Guidelines for other repositories
+
+`tools/wikitool export guidelines` renders the pages this filter selects into one generated
+`GUIDELINES.md` for the repositories this instance captured (`raw/CONTRACT.md`). The stack defines
+no type or field for a guideline - which pages are guidelines is this instance's decision, and it
+is written down here and nowhere else.
+
+{The selection, as `search` predicates - for example `--tag guideline` - or "none" if this
+instance exports no guidelines.}
+
 ## Keeping this file honest
 
 Change it when a convention actually changes. `wikitool doctor` FAILs on a missing or unfilled