Editions become changeable — losslessly

Eric hit a diff version-disagreement and found there was no way to
revisit a set edition: the Titles pick-edition button only appeared
while the version was UNSET. It now shows as "change edition" on
version_auto/version_approved rows — and reopening the ballot no
longer clears the current pick, because change must be lossless:
abandoning the ballot keeps the approved edition, the lingering id is
inert while ambiguous (is_confident_version gates diff and upload),
and the next decision overwrites or clears it.

Help documents the other half of the disagreement story: the pipeline
NEVER edits a version already set on a BGG collection entry (the
additive-only rule), so a diff disagreement is resolved either by
changing the pipeline's pick here or by fixing the entry by hand on
BGG.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016jXZFSTZQKzAC8fqpWSz9g

tests/test_review.py

@@ -761,3 +761,34 @@ def test_research_clears_the_previous_games_version(tmp_path):
     assert row["version_status"] == ""
     assert row["version_id"] == "" and row["version_name"] == ""
     assert row["version_candidates_json"] == "[]"
+
+
+def test_reopening_a_version_ballot_keeps_the_current_pick(tmp_path):
+    """Change-edition must be lossless: opening the full printing list on
+    an approved row keeps the pick until a new decision, and the lingering
+    id is inert while ambiguous."""
+    from bggpipe.models import is_confident_version
+
+    cfg = _setup(
+        tmp_path,
+        [
+            _row(
+                title_raw="Wingspan",
+                match_status="approved",
+                bgg_id="266192",
+                version_status="version_approved",
+                version_id="465063",
+                version_name="English first edition",
+            )
+        ],
+    )
+    session = ReviewSession(
+        cfg, console=quiet_console(), input_fn=scripted(), client=fixture_client()
+    )
+    row = session.rows[0]
+    assert session.open_version_ballot(row) > 1
+    assert row["version_status"] == "version_ambiguous"
+    assert row["version_id"] == "465063"  # survives until a new choice
+    assert not is_confident_version(row)  # but inert for diff/upload
+    session.decide_version(row, None)  # "can't tell" clears it properly
+    assert row["version_id"] == ""