fix(u6): fold the cold code-review panel — four-arm convergence on three surface clauses

/heid-code-review panel 01M35CK8YKEKMV7T15JXEF6A8N, verdict NOT drift-zero.
Three findings arrived from all four arms independently, and they share a
shape: a contract clause written as prose and never converted into an
assertion. That is the lens working.

- The panel dropped the added date the contract promised to show.
- `bench ls` printed no ids, and the URL it printed was truncated to 52 columns
  so the line was not pasteable into `bench state|rm`. The test's docstring
  claimed it printed ids and asserted nothing of the kind.
- `bench import` printed the description instead of the raw URL beside each
  normalized id, hiding the collapse the clause exists to expose.
- An IPv6 literal lost its brackets: http://[::1]:8080/a normalized to
  http://::1:8080/a, a broken identity that no re-post can match. Bracketed
  literals are re-wrapped; an unbracketed one is refused rather than guessed.
- A deeply-nested JSON RecursionError escaped read_benches' except pair. The
  byte cap does not help -- 200k open brackets is 200 KB.
- An empty board hid the whole benches panel, registration form included.
- The link refusal classified by captured-text emptiness, which bash can erase;
  it now answers with a B:/N sentinel so no name reads as "not a booth".

INV-4's tie-break falsifier could not fail: _write_all serializes with
sort_keys=True, so both insertion orders came back already id-sorted and
removing the tie-break left the test green. It now calls order_benches
directly. Same class as the five vacuous U4 falsifiers, found by a cold reader
rather than by us.

Also from the arms' per-invariant vacuity pass: INV-6 had no vector pinning a
non-default port as part of the identity; INV-3 asserted only that links/ was
absent; INV-8's hashed sequence omitted a read verb; INV-9's AST walk is
defeated by a string import. All closed.

Contract amended where the code was right: `updated` means last mutation, the
id cap is write-only because the id is the locator controls post back, INV-8's
file list includes the lock sidecar it always mandated. Every line number is
out of the prose -- the panel found two already stale.

565 -> 593 tests. Nothing declined.

scripts/booth

@@ -218,12 +218,20 @@ booth_src() {
 # the board's dead-row marker and `bench import` use that same function and a
 # second implementation in the shell would classify the host-agnostic and
 # percent-encoded cases differently (INV-2).
+# Prints `B:<name>` for a booth URL and `N` for anything else.
+#
+# A SENTINEL, NOT AN EMPTY STRING. Command substitution strips trailing
+# newlines, so a predicate that answers with the bare name cannot distinguish
+# "not a booth" from "a booth whose name bash just erased" — and the guard
+# then fails OPEN on that edge, which is the one direction a guard must never
+# fail. The prefix makes the answer unambiguous whatever the name contains.
 booth_target_of() {
   BOOTH_SRC="$(booth_src)" BOOTH_Q="$1" python3 -c '
 import os, sys
 sys.path.insert(0, os.environ["BOOTH_SRC"])
 from booth.links import booth_target          # stdlib only — no venv needed
-sys.stdout.write(booth_target(os.environ["BOOTH_Q"]) or "")
+name = booth_target(os.environ["BOOTH_Q"])
+sys.stdout.write("N" if name is None else "B:" + name)
 '
 }
 
@@ -344,6 +352,13 @@ case "$cmd" in
       } >&2
       exit 3
     fi
+    case "$refused_name" in
+      N) refused_name="" ;;
+      B:*) refused_name="${refused_name#B:}" ;;
+      *)
+        echo "booth link: the booth check answered something unrecognised; nothing was posted." >&2
+        exit 3 ;;
+    esac
     if [ -n "$refused_name" ]; then
       {
         echo "booth link: that is a booth, and a booth announces itself now."
@@ -463,7 +478,12 @@ def die(msg, code=2):
 def row(b):
     # ONE LINE PER BENCH, in the rendered order — state first, so a retired
     # bench sinks, then name, then id as a total tie-break (INV-4).
-    return "%-9s %-28s %-52s %s" % (b.state, b.name[:28], b.url[:52], b.owner)
+    # THE ID IS PRINTED WHOLE AND UNTRUNCATED, because it is the locator
+    # `bench state` and `bench rm` take: a truncated one is not an id, it is a
+    # string that looks like one and silently addresses nothing. The name and
+    # the added date are the truncatable columns.
+    return "%-9s  %-10s  %-16s  %-24s  %s" % (
+        b.state, b.added[:10], b.owner[:16], b.name[:24], b.id)
 
 if sub == "add":
     if len(argv) < 2: die("bench add <url> <name>")
@@ -478,6 +498,9 @@ elif sub == "ls":
         die("the registry could not be read: %s" % err, 3)
     if not benches:
         print("no benches registered yet")
+    else:
+        print("%-9s  %-10s  %-16s  %-24s  %s"
+              % ("STATE", "ADDED", "OWNER", "NAME", "ID (pass to state|rm)"))
     for b in benches:
         print(row(b))
 elif sub in ("state", "rm"):
@@ -518,7 +541,13 @@ elif sub == "import":
     print("CANDIDATES — would be registered (%d rows, %d distinct):"
           % (len(candidates), len({i for i, _ in candidates})))
     for i, e in candidates:
-        print("  %-52s %s" % (i, e["desc"][:60]))
+        # THE NORMALIZED ID BESIDE THE RAW URL, which is the whole point of the
+        # proposal: five rows of `talk` collapsing to one is only visible if you
+        # can see which five raw URLs produced the one id. The description is
+        # the thing to drop here, not the URL.
+        print("  %-52s %s" % (i, e["url"]))
+        if e["desc"]:
+            print("  %-52s   %s" % ("", e["desc"][:70]))
     print()
     print("REFUSED — normalization said no (%d):" % len(refused))
     for e, why in refused: