test: prune duplicate tests, re-sight two blind coverage guards

Follow-up to a fan-out audit of the whole test suite (742 tests, 21
read-only assessors + synthesis). Two clusters of the audit were
actioned here; the #66 hashing-removal cohort it surfaced is left for
the #66 scope, and the RED-first doc-rot sweep is deferred.

§2 — true duplicates removed (each kept test is a strict superset or
identical fixture+assertions of the deleted one):
- ailang-check param_in_reject_message_names_allowed_set (kept the
  _renders_allowed_set_in_ailang_syntax superset)
- ailang-check cross_module_pat_ctor_typedriven_resolves (kept ct2_;
  shared cross_module_ws helper retained, 2 other callers)
- ailang-core mq1_qualified_instancedef_class_accepted (kept ct1_)
- ail e2e bool_to_str_emits_true_branch (kept the rc-stats superset)
- ail loop_recur_str adt-leg guard (the standalone heap pin owns it;
  dropped the dangling header reference too)
- ailang-check over_strict_mode_silent_when_param_is_borrow (its
  assertion is subsumed by explicit_fn_with_no_uses_is_clean; its own
  doc claimed a "borrowing body" the Lit body never provided)

§4 — meta-guards that had gone partially blind re-sighted:
- spec_drift::spec_mentions_every_def_kind now pushes Class/Instance
  exemplars and asserts their `(class `/`(instance` anchors; the
  "wait for 22b.4" exclusion was stale (anchors shipped in e809f45).
- schema_coverage now tracks Term::New (VariantTag + EXPECTED +
  visitor insert); the new_*/raw_buf_* fixtures already exercise it,
  so the "no fixture emits new" exclusion was stale.
- prose doc_wrap_widow_control_skips_when_combined_too_long was
  tautological: its 32/32/42-char words gave combined=75<=80, so
  widow control actually fired. Rebuilt the fixture (short head + two
  40-char words → combined=81>80) so it hits the real skip branch,
  and added the missing "last line stays 1 word" assertion. The
  obvious 2-word fixture does NOT work — it skips via the
  prev_words<2 branch, not the combined-over-budget branch.

ailang-check 124->121, ailang-core 55->54, e2e 102->101,
loop_recur_str 4->3; spec_drift 8 green, schema_coverage green,
prose lib 63 green.

crates/ailang-core/tests/spec_drift.rs

@@ -14,7 +14,8 @@
 use std::collections::BTreeMap;
 
 use ailang_core::ast::{
-    ConstDef, Ctor, Def, FnDef, Literal, NewArg, Pattern, Suppress, Term, Type, TypeDef,
+    ClassDef, ConstDef, Ctor, Def, FnDef, InstanceDef, Literal, NewArg, Pattern, Suppress, Term,
+    Type, TypeDef,
 };
 use ailang_core::FORM_A_SPEC;
 
@@ -293,10 +294,27 @@ fn spec_mentions_every_def_kind() {
         drop_iterative: false,
         param_in: BTreeMap::new(),
     };
+    let class_def = ClassDef {
+        name: "C".into(),
+        param: "a".into(),
+        superclass: None,
+        methods: vec![],
+        doc: None,
+    };
+    let instance_def = InstanceDef {
+        class: "C".into(),
+        type_: Type::int(),
+        methods: vec![],
+        doc: None,
+    };
     let exemplars: Vec<(&str, Def)> = vec![
         ("(fn ", Def::Fn(fn_def)),
         ("(const ", Def::Const(const_def)),
         ("(data ", Def::Type(type_def)),
+        // class/instance gained prose projection in e809f45 (form-a.tidy):
+        // FORM_A_SPEC now carries `(class ` / `(instance ` anchors.
+        ("(class ", Def::Class(class_def)),
+        ("(instance", Def::Instance(instance_def)),
     ];
 
     for (anchor, def) in exemplars {
@@ -304,12 +322,6 @@ fn spec_mentions_every_def_kind() {
             Def::Fn(_) => "fn",
             Def::Const(_) => "const",
             Def::Type(_) => "type",
-            // class/instance Def variants exist but are
-            // not yet anchored in the prose-spec block. Once 22b.4
-            // adds prose projection for them, the FORM_A_SPEC text
-            // gains `(class ` / `(instance ` anchors and this match
-            // will be exercised. For 22b.1 the exemplars list above
-            // does not produce these variants.
             Def::Class(_) => "class",
             Def::Instance(_) => "instance",
         };