feat: implement the wiki field in the issue domain

format.md listed `wiki:` among the domain fields, between depends and
origin, and issue.py had never heard of it. The field fell into extra and
rendered with the foreign keys — sorted in after the sync fields, which
the same document forbids one line below the table. Written without
brackets it parsed as a single string, and nothing but a text editor
could set it.

Implemented rather than de-documented: page_ls.py --titles already
prints these titles, so the field was designed and only unwired.
DOMAIN_KEYS and LIST_KEYS learn it, Issue carries it, and issue_new.py
gets a repeatable --wiki flag.

Titles only, as the format says: no path, no sub_url, no lookup. The
tracker has no field for it, so it is never sent and a pull does not
bring it back — format.md now says so.

Closes #32

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

skills/issue/scripts/issue.py

@@ -25,6 +25,7 @@ domain has. The file name is the id:
     assignees: [naudachu]
     milestone: v0.2
     depends: [migrate-schema]
+    wiki: [Simple Chains/Ideas/Chain core]
     origin: gitea
     gitea: owner/repo#42
     synced: 2026-08-07T18:40:00Z
@@ -113,8 +114,9 @@ ISSUE_ROOT = store_root()
 
 # Domain-owned metadata, in render order. Foreign keys render after these,
 # sorted, so the sync layer can add fields without touching this list.
-DOMAIN_KEYS = ["id", "state", "labels", "assignees", "milestone", "depends", "origin"]
-LIST_KEYS = {"labels", "assignees", "depends"}
+DOMAIN_KEYS = ["id", "state", "labels", "assignees", "milestone", "depends",
+               "wiki", "origin"]
+LIST_KEYS = {"labels", "assignees", "depends", "wiki"}
 STATES = ("open", "closed")
 
 # `origin` is "does this issue exist anywhere but here" — a fact about the
@@ -247,8 +249,8 @@ class Issue(object):
     """One unit of work. `extra` holds metadata this layer does not own."""
 
     def __init__(self, id="", title="", body="", state="open", labels=None,
-                 assignees=None, milestone="", depends=None, origin=LOCAL,
-                 extra=None):
+                 assignees=None, milestone="", depends=None, wiki=None,
+                 origin=LOCAL, extra=None):
         self.id = id
         self.title = title
         self.body = body
@@ -257,6 +259,10 @@ class Issue(object):
         self.assignees = list(assignees or [])
         self.milestone = milestone or ""
         self.depends = list(depends or [])
+        # Page TITLES this work is written up in — names for documents, which
+        # is why they are domain-owned. What a title resolves to is /tea:page's
+        # business, and this layer never asks: no path, no URL, no lookup.
+        self.wiki = list(wiki or [])
         self.origin = origin or LOCAL
         self.extra = dict(extra or {})
 
@@ -302,7 +308,7 @@ class Issue(object):
                    state=meta.get("state") or "open",
                    labels=lst("labels"), assignees=lst("assignees"),
                    milestone="" if ms == "none" else ms,
-                   depends=lst("depends"),
+                   depends=lst("depends"), wiki=lst("wiki"),
                    origin=meta.get("origin") or LOCAL, extra=extra)
 
     def to_text(self):
@@ -314,6 +320,7 @@ class Issue(object):
             "assignees": self.assignees,
             "milestone": self.milestone or "none",
             "depends": self.depends,
+            "wiki": self.wiki,
             "origin": self.origin,
         })
         body = self.body.strip() or "(no body)"