fix: comparison and source pages accept the sources: cite add writes; sources may cite sources (#173)

Files changed:
- CHANGES.md
- VERSION
- instructions/wiki-ingest/SKILL.md
- kb/CONTRACT.md
- tools/CONTRACT.md
- tools/chemenu/commands/cite_cmd.py
- tools/chemenu/commands/xref.py
- tools/chemenu/tests/test_cite_cmd.py
- tools/chemenu/tests/test_page_ops.py
- tools/chemenu/tests/test_type_resolver.py
- tools/chemenu/tests/test_xref.py
- types/comparison.md
- types/comparison.schema.yaml
- types/source.md
- types/source.schema.yaml

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

types/comparison.md

@@ -4,7 +4,7 @@ name: comparison
 description: Structured type for comparison pages that set several entities or approaches against one another
 schema: types/comparison.schema.yaml
 base_dir: comparisons
-page_ref_fields: [entities, related]
+page_ref_fields: [entities, related, sources]
 guidance: types/comparison.guidance.md
 ---
 
@@ -24,6 +24,7 @@ and how to write a conforming page is [types/comparison.guidance.md](comparison.
 | `created` | Yes | Creation date (YYYY-MM-DD) |
 | `entities` | Yes | Titles of the entities compared |
 | `related` | No | Declared outbound edges - one `compares-with` edge per subject, written by `wikitool xref add` |
+| `sources` | No | Titles of the source pages cited on this page, written by `wikitool cite add` |
 | `summary` | Yes | One-liner for `kb/index.md` |
 
 ## Template

types/comparison.schema.yaml

@@ -38,6 +38,13 @@ properties:
       provenance-style list, so without this one the edge the page exists to
       make would live only in hand-written prose - which is the thing
       instructions/link-taxonomy.md was built to end.
+  sources:
+    type: array
+    items:
+      type: string
+    description: >-
+      Source page titles cited on this page, written by `wikitool cite add`.
+      Optional, so a comparison that cites nothing keeps validating without it.
   summary:
     type: string
     description: 1-line summary for index.md

types/source.md

@@ -6,7 +6,7 @@ schema: types/source.schema.yaml
 subtype_field: source_type
 base_dir: sources
 title_prefix: "Source - "
-page_ref_fields: [entities, concepts]
+page_ref_fields: [entities, concepts, sources]
 capture_fields: [fidelity, authority]
 guidance: types/source.guidance.md
 layout:
@@ -42,6 +42,7 @@ how to write a conforming page is [types/source.guidance.md](source.guidance.md)
 | `tags` | No | Navigation tags for categorization |
 | `entities` | No | Titles of the entities mentioned in this source |
 | `concepts` | No | Titles of the concepts mentioned in this source |
+| `sources` | No | Titles of *other* source pages this source cites, written by `wikitool cite add` - never its own title |
 | `summary` | Yes | One-liner for `kb/index.md` |
 
 ## Template

types/source.schema.yaml

@@ -72,6 +72,15 @@ properties:
     items:
       type: string
     description: Concept titles mentioned in this source
+  sources:
+    type: array
+    items:
+      type: string
+    description: >-
+      Other source pages this source cites, written by `wikitool cite add`.
+      Never this page's own title - a citation of one of its own raw files
+      leaves the field untouched. Optional, so a source that cites no other
+      source keeps validating without it.
   summary:
     type: string
     description: 1-line summary for index.md