fix: address code-review findings on lineclass_scan test PR

- Remove stale IncomingAnchorEdges audit entry (exemption already
  present at internal/lsp/rename.go:437)
- Add internal/rules/listscan to the approved-helpers list in the
  architecture hub and audit checklist, restoring the clearance that
  was deleted when the 2026-06-21 audit entry was compressed
- Add TestContainsFold directly testing the sliding-window
  case-insensitive searcher (boundary cases: match at pos 0, middle,
  last window; no match; needle longer than line; empty line)
- Add end-of-input success case to TestScanTagName

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VwsEmnkHJvLoaj8imqQRjJ

Author: claude

docs/development/architecture-audit.md

@@ -286,9 +286,5 @@ PR #690 are in range.
 - `internal/lint/layer0_html.go` — 7
   unexported helpers. PR #701 in-flight.
 
-- `internal/lsp/rename.go` —
-  `IncomingAnchorEdges` lacks a test or
-  "// no test by design" exemption.
-
 [2606260614]: ../../plan/2606260614_arch-fix-lineclass-scan-helper-tests.md
 [2606260615]: ../../plan/2606260615_arch-fix-cuelite-engine-helper-tests.md

docs/development/architecture/audit-checklist.md

@@ -211,8 +211,8 @@ explicit mention here:
 - **A rule package importing another
   rule package** — always a DIP
   blocker. Helpers belong in
-  `internal/mdtext` or
-  `internal/rules/astutil`.
+  `internal/mdtext`, `internal/rules/astutil`,
+  or `internal/rules/listscan`.
 - **`cmd/mdsmith/main.go` past ~1000
   lines** — handler bodies have crept
   in; relocate to `internal/engine` or

docs/development/architecture/index.md

@@ -275,8 +275,8 @@ caught and the reasons we reject them:
   attracts unrelated code.
 - **A rule package importing another rule
   package.** Rules share helpers via
-  `internal/mdtext` or
-  `internal/rules/astutil`; reaching
+  `internal/mdtext`, `internal/rules/astutil`,
+  or `internal/rules/listscan`; reaching
   sideways into a sibling rule binds
   release cycles that should stay
   independent.

internal/lint/lineclass_scan_test.go

@@ -190,6 +190,16 @@ func TestHTMLType6AndClose(t *testing.T) {
 	assert.False(t, containsType1Close([]byte("short")), "shorter than any closer")
 }
 
+func TestContainsFold(t *testing.T) {
+	needle := []byte("</pre>")
+	assert.True(t, containsFold([]byte("</PRE>"), needle), "match at position 0")
+	assert.True(t, containsFold([]byte("x</Pre>y"), needle), "match in middle")
+	assert.True(t, containsFold([]byte("x</PRE>"), needle), "match at last window")
+	assert.False(t, containsFold([]byte("x</em>y"), needle), "no match")
+	assert.False(t, containsFold([]byte("</pr"), needle), "needle longer than line")
+	assert.False(t, containsFold([]byte(""), needle), "empty line")
+}
+
 func TestContainerMarkerScanners(t *testing.T) {
 	assert.Equal(t, 2, blockquoteMarker([]byte("> x")))
 	assert.Equal(t, 1, blockquoteMarker([]byte(">x")), "marker with no following space")
@@ -378,6 +388,11 @@ func TestScanTagName(t *testing.T) {
 	// Empty input.
 	_, ok = scanTagName([]byte(""), 0)
 	assert.False(t, ok)
+
+	// Name runs to end of input (no terminator byte).
+	i, ok = scanTagName([]byte("img"), 0)
+	assert.True(t, ok)
+	assert.Equal(t, 3, i)
 }
 
 // TestScanAttribute pins the attribute scanner.