fix(tests): the repeat tail is the middle state now, not the opened one (#4100)

CI run 6943: 11 failures, two causes, both existing guards correctly catching
the behaviour change rather than defects in it.

TEN were `_SEEN_TAIL = "You saw it earlier this session"`. Every one of those
tests drives an arm with `exclude_rule_ids` alone — the NAMING ledger — which
since this change is the middle state, not the opened one. That is the whole
point of the step: `seen` stopped meaning "you saw it". The constant now holds
the middle tail, so each test keeps asserting exactly what it was written to
assert (a repeat gets a line distinct from a first surfacing) against the
wording that is now true.

Added `_HELD_TAIL` and a negative assertion with it: neither call names an
opened ledger, so neither may claim the session read anything. That catches
`held` defaulting true, which would have every repeat assert the strongest of
the three claims on no evidence — and none of the ten existing tests would
have noticed.

THE ELEVENTH was my own test edit being wrong, not the code. I asserted
`held_rule_ids` would appear in `re.findall(r"printf '([a-z_]+)=", defs)`, but
`scribe_held_query` spells it `printf '&held_rule_ids=`, and the leading `&`
means that regex never matches it. The regex enumerates SCOPE keys — the
alternatives that open a query — and the ledger key is appended to a query
that already has one. Two different contracts that happened to share a file,
so they are now asserted separately and the difference is written down.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

tests/test_write_path_trigger.py

@@ -942,9 +942,12 @@ def test_route_reads_every_arg_the_hook_sends():
     # helper so its ageing and format cannot drift from the naming ledger's.
     assert "scribe_held_query" in hook, "hook no longer sends the opened ledger"
     defs = (HOOK.parent / "scribe_defs.sh").read_text()
-    assert set(re.findall(r"printf '([a-z_]+)=", defs)) == {
-        "repo", "project_id", "held_rule_ids",
-    }
+    assert set(re.findall(r"printf '([a-z_]+)=", defs)) == {"repo", "project_id"}
+    # Its own leading `&` — it is appended to a query that already carries a
+    # scope key, rather than being one of the alternatives that opens one.
+    assert "printf '&held_rule_ids=" in defs, (
+        "the opened ledger's query key is no longer spelled in the helper"
+    )
 
 
 def test_route_resolves_repo_to_a_project_not_to_a_location_filter():