fix(port): check-citations was red, and its selftest BROKEN, on a clean tree

Two independent defects, both making the script report a correct checkout as
wrong. Neither is new; both were invisible because nobody ran it here.

1. `export/` is the exporter's OUTPUT and is gitignored (`/export*/`). A
   checkout where nobody has run the exporter has no `export/` at all, so the
   four `DECISIONS.md`/`BLOCKED.md` citations of `export/manifest.json` and
   `export/screens/...` landed in "resolve NOWHERE" and the check exited 1 --
   red for a state no edit can fix, which is the exact shape its own docstring
   says it exists to avoid. `check-capture-citations` learned this for
   `docs/re/captures/`; same rule now: absent BECAUSE UNBUILT is reported,
   absent while the tree IS built still fails. Verified both ways -- `mkdir
   export` and the same four go back to failing.

2. The selftest's peer-branch fixture cited
   `docs/re/f5-a-press-snaps-the-plate.md`, which the consolidation made an
   ordinary local file. The fixture stopped testing the scanner and started
   reporting it broken; `PEER_REFS` also still named
   `origin/auto/frame-blend-draw-path`, a branch that no longer exists. The
   selftest now FINDS a peer-only path at runtime, and where none exists -- the
   normal case on a clean checkout, measured: zero -- it says the class is empty
   here rather than claiming a failure. The class itself stays: the next topic
   branch that lands a finding recreates the condition exactly.

Measured: check 123 citations, 119 resolve, 4 unbuilt, 0 nowhere, exit 0 (was
exit 1). Selftest ok (was 🔴 BROKEN, on `main` too). The new generated-tree case
was confirmed to FAIL against the unfixed function first.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/port/check-citations

@@ -36,7 +36,60 @@ CITE = re.compile(
     r"`?((?:docs|crates|port|tools|authored|export)/[\w./-]+"
     r"\.(?:md|rs|gd|json|txt|py|tsv|csv))`?"
 )
-PEER_REFS = ("origin/auto/frame-blend-draw-path", "origin/main")
+# ⚠️ `origin/auto/frame-blend-draw-path` used to head this list and NO LONGER
+# EXISTS -- the consolidation merged it and the branch was removed. The class is
+# kept because it is about the workflow, not about that one branch: the next
+# topic branch that lands a finding recreates the condition exactly. What must
+# not happen again is the selftest asserting the class against a fixture path
+# that has since become an ordinary local file, which is how it came to print
+# 🔴 BROKEN on a correct checkout. It now finds its own fixture, or says the
+# condition does not exist here.
+PEER_REFS = ("origin/main",)
+
+
+def a_peer_only_path() -> str | None:
+    """A path carried by a PEER_REF but absent from this working tree.
+
+    The selftest needs a REAL one: a hardcoded fixture silently stops testing
+    the moment that file lands locally, and then reports the scanner broken
+    instead of itself. On a clean, up-to-date checkout there is usually no such
+    path at all -- which is not a failure, it is the class being empty here.
+    """
+    for ref in PEER_REFS:
+        out = subprocess.run(["git", "ls-tree", "-r", "--name-only", ref],
+                             capture_output=True, text=True)
+        for f in out.stdout.splitlines():
+            if f.endswith((".md", ".rs", ".gd", ".json", ".txt", ".py",
+                           ".tsv", ".csv")) and not os.path.exists(f):
+                return f
+    return None
+
+
+def gitignored(path: str) -> bool:
+    """Is this path deliberately untracked? Pattern match -- existence not needed."""
+    return subprocess.run(["git", "check-ignore", "-q", path],
+                          capture_output=True).returncode == 0
+
+
+def unbuilt(path: str) -> bool:
+    """A citation of GENERATED output whose tree has not been built here.
+
+    🔴 THE THIRD ABSENCE, AND IT IS NOT AN ERROR. `export/` is the exporter's
+    output and is gitignored (`.gitignore` `/export*/`). A checkout where nobody
+    has run the exporter has no `export/` at all, so the four `DECISIONS.md` and
+    `BLOCKED.md` citations of `export/manifest.json` and `export/screens/...`
+    were counted as "resolve NOWHERE" and this check was red on a clean tree --
+    for a state no edit can fix, which is precisely the shape its own docstring
+    says it exists to avoid.
+
+    `check-capture-citations` already learned this for `docs/re/captures/`.
+    Same rule here: absent BECAUSE UNBUILT is reported; absent while the tree
+    IS built is a real broken citation and still fails.
+    """
+    if not gitignored(path):
+        return False
+    root = path.split("/")[0]
+    return not os.path.exists(root)
 
 
 def on_a_ref(path: str) -> str | None:
@@ -49,7 +102,7 @@ def on_a_ref(path: str) -> str | None:
 
 
 def scan(files):
-    resolves, peer, nowhere = 0, {}, {}
+    resolves, peer, nowhere, ungenerated = 0, {}, {}, {}
     for p in files:
         try:
             text = open(p, encoding="utf-8").read()
@@ -58,11 +111,13 @@ def scan(files):
         for m in sorted(set(CITE.findall(text))):
             if os.path.exists(m):
                 resolves += 1
+            elif unbuilt(m):
+                ungenerated.setdefault(m, p)
             elif (ref := on_a_ref(m)):
                 peer.setdefault(m, (p, ref))
             else:
                 nowhere.setdefault(m, p)
-    return resolves, peer, nowhere
+    return resolves, peer, nowhere, ungenerated
 
 
 def main() -> int:
@@ -82,28 +137,51 @@ def main() -> int:
         # exists) and does not resolve here (the reader still gets nothing), and
         # a scanner that collapsed it into either would make the flag meaningless
         # while still passing the two checks above.
+        peer_probe = a_peer_only_path()
         peerfile = os.path.join(tmp, "peer.md")
-        open(peerfile, "w").write("see `docs/re/f5-a-press-snaps-the-plate.md`\n")
+        open(peerfile, "w").write("see `%s`\n" % (peer_probe or "docs/port/PORT-MISSION.md"))
-        rp, pp, np_ = scan([peerfile])
+        # The FOURTH class: generated output whose tree is not built here.
+        # It has to be told apart from "resolves nowhere", which is the whole
+        # point -- a scanner that lumped them together is what made this check
+        # red on a clean checkout.
+        genfile = os.path.join(tmp, "gen.md")
+        open(genfile, "w").write("see `export/screens/title/main_menu.json`\n")
 
-        _, _, nb = scan([bad])
+        rp, pp, np_, gp = scan([peerfile])
-        r, _, ng = scan([good])
+
+        _, _, nb, _ = scan([bad])
+        r, _, ng, _ = scan([good])
+        rg, pg, ng2, gg = scan([genfile])
         caught   = len(nb) == 1
         passed   = len(ng) == 0 and r == 1
-        peer_ok  = len(pp) == 1 and rp == 0 and len(np_) == 0
+        # None == the class is empty in this checkout, not that it is broken.
-        ok = caught and passed and peer_ok
+        peer_ok = (len(pp) == 1 and rp == 0 and len(np_) == 0 and len(gp) == 0) \
+                  if peer_probe else None
+        # Only meaningful while `export/` is absent; if someone ran the exporter
+        # in this checkout the citation legitimately resolves instead.
+        gen_ok = (len(gg) == 1 and len(ng2) == 0 and len(pg) == 0) \
+                 if not os.path.exists("export") else (rg == 1)
+        ok = caught and passed and gen_ok and peer_ok is not False
         print("selftest: planted dangling caught=%s, real citation passed=%s, "
-              "peer-branch classed separately=%s -> %s"
+              "peer-branch classed separately=%s, unbuilt-generated classed "
-              % (caught, passed, peer_ok, "ok" if ok else "🔴 BROKEN"))
+              "separately=%s -> %s"
-        if not peer_ok:
+              % (caught, passed,
+                 "n/a (no peer-only path exists here)" if peer_ok is None
+                 else peer_ok,
+                 gen_ok, "ok" if ok else "🔴 BROKEN"))
+        if not gen_ok:
+            print("   🔴 a citation of unbuilt generated output must NOT be "
+                  "dangling; got resolves=%d peer=%d nowhere=%d ungenerated=%d"
+                  % (rg, len(pg), len(ng2), len(gg)))
+        if peer_ok is False:
             print("   🔴 --for-merge cannot mean anything if the peer class is "
                   "not distinguished; got resolves=%d peer=%d nowhere=%d"
                   % (rp, len(pp), len(np_)))
         return 0 if ok else 2
 
     files = sorted(glob.glob("docs/port/*.md"))
-    resolves, peer, nowhere = scan(files)
+    resolves, peer, nowhere, ungenerated = scan(files)
-    total = resolves + len(peer) + len(nowhere)
+    total = resolves + len(peer) + len(nowhere) + len(ungenerated)
     print("citations of repo paths in docs/port/*.md: %d" % total)
     print("  resolve here                : %d" % resolves)
     # 🔴 --for-merge TURNS THE PEER CLASS INTO A FAILURE.
@@ -130,6 +208,13 @@ def main() -> int:
         print("   After this merges they resolve NOWHERE -- the reader gets a dead")
         print("   path. Land the finding first and make it a dependency of this PR.")
         return 1
+    if ungenerated:
+        print("  not built in this checkout  : %d  (reported, not failed)"
+              % len(ungenerated))
+        for m, src in sorted(ungenerated.items()):
+            print("      %-52s <- %s" % (m, os.path.basename(src)))
+        print("      run the exporter and these resolve; a path still missing")
+        print("      afterwards IS dangling and fails below.")
     if nowhere:
         print("  🔴 resolve NOWHERE          : %d" % len(nowhere))
         for m, src in sorted(nowhere.items()):