feat: Prosa ist kein Identifier - Link-Taxonomie als Enum, generierte Regionen mit Markern (4.0.0)

Files changed:
- .gitea/workflows/ci.yml
- AGENTS.md
- CHANGES.md
- VERSION
- instructions/CONTRACT.md
- instructions/link-taxonomy.md
- instructions/migrations/4.0.0-link-taxonomy.md
- instructions/setup-instance.md
- kb/CONTRACT.md
- kb/CONVENTIONS.md
- kb/CONVENTIONS.md.template
- kb/comparisons/COLLECTION.md
- kb/concepts/COLLECTION.md
- kb/entities/COLLECTION.md
- kb/sources/COLLECTION.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/blocks.py
- tools/chemenu/cli.py
- tools/chemenu/commands/cite_cmd.py
- tools/chemenu/commands/dist_cmd.py
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/links_cmd.py
- tools/chemenu/commands/migrate_cmd.py
- tools/chemenu/commands/new_page.py
- tools/chemenu/commands/page_ops.py
- tools/chemenu/commands/run_budget.py
- tools/chemenu/commands/xref.py
- tools/chemenu/conventions.py
- tools/chemenu/corpus_diff.py
- tools/chemenu/frontmatter_io.py
- tools/chemenu/kb_collections.py
- tools/chemenu/kb_state.py
- tools/chemenu/links.py
- tools/chemenu/lint_core.py
- tools/chemenu/provenance.py
- tools/chemenu/sections.py
- tools/chemenu/tests/conftest.py
- tools/chemenu/tests/test_blocks.py
- tools/chemenu/tests/test_cite_cmd.py
- tools/chemenu/tests/test_conventions.py
- tools/chemenu/tests/test_dist_cmd.py
- tools/chemenu/tests/test_doctor.py
- tools/chemenu/tests/test_migrate_cmd.py
- tools/chemenu/tests/test_new_page.py
- tools/chemenu/tests/test_pipeline_l0.py
- tools/chemenu/tests/test_types_cmd.py
- tools/chemenu/tests/test_xref.py
- types/concept.schema.yaml
- types/entity.md
- types/entity.schema.yaml
- types/instruction.schema.yaml
- types/type-spec.md
- work/link-taxonomy-migration/README.md
- work/link-taxonomy-migration/plan.md

kb/comparisons/COLLECTION.md

@@ -1,5 +1,7 @@
 ---
 profile: comparisons
+outbound:
+  any: [compares-with, contrasts, see-also]
 required_by_stack: false
 ---
 
@@ -37,11 +39,22 @@ alphabetically.
 - State the trade-off, not a winner. Where a recommendation is genuinely warranted, scope it:
   "for X workload", not "better".
 
+## Authorised labels
+
+The `outbound:` block above is what `wikitool lint` and `xref add` check: which labels a page in
+this collection may use, per destination. The catalogue they are drawn from - and what each one
+asserts - is [instructions/link-taxonomy.md](../../instructions/link-taxonomy.md), which binds
+nothing on its own.
+
+Narrow for the opposite reason: a comparison's substance is its table, and its links to the compared subjects are the one relationship it asserts.
+
+Adding a label here is a deliberate contract change, not a way around a refusal.
+
 ## Outbound linking
 
-A comparison links to every subject with `related to`, and each subject links back. Comparison
-pages are **exempt from the orphan check** - they are reached through `index.md` rather than
-through inbound prose links.
+A comparison links to every subject with `compares-with`. The subjects do not have to link back:
+a comparison is reached through the catalog, and each subject's inbound view renders the edge
+anyway. Comparison pages are **exempt from the orphan check** for the same reason.
 
 ## What does not belong here