Deduplicate the host audio/UI code and scrub history from comments

Extract a RAII RenderEndpoint that owns the enumerator/endpoint/client/
render-event/buffer for both AudioMirror::run_hooked and run_loopback,
replacing two hand-rolled setup+teardown blocks and their two identical
fail lambdas with one set_error helper; every COM object now frees on
each exit path automatically.

Route audio_format_verifier's mono decode through the shared
correlate_detail::decode_layout instead of a second copy, and read the
debug env var via GetEnvironmentVariableA (drops the getenv C4996).

Fold the near-identical read_frame/read_pixel staging-copy setup in
SharedTextureSource into one map_staging_copy, and the three separate
case-insensitive filter helpers (log/injection panels) into
ui/text_match.hpp.

Comments: drop game-name anecdotes and "the old code"/version phrasing;
genericize the override-file example; fix a stale heartbeat-interval
note. Behavior unchanged (host tests + mock_game_test pass).

host/src/ui/text_match.hpp

@@ -0,0 +1,31 @@
+// Small case-insensitive text helpers shared by the host panels' filter boxes, so
+// "error" matches "ERROR" everywhere consistently. ASCII-fold only (the UI filters
+// are typed ASCII); non-ASCII bytes compare as-is.
+#pragma once
+
+#include <cctype>
+#include <string>
+
+namespace coop
+{
+
+inline std::string ascii_lower(std::string s)
+{
+	for (char& c : s)
+	{
+		c = static_cast<char>(std::tolower(static_cast<unsigned char>(c)));
+	}
+	return s;
+}
+
+// True when `needle` is empty or a case-insensitive substring of `haystack`.
+inline bool contains_ci(const std::string& haystack, const char* needle)
+{
+	if (needle == nullptr || needle[0] == '\0')
+	{
+		return true;
+	}
+	return ascii_lower(haystack).find(ascii_lower(needle)) != std::string::npos;
+}
+
+} // namespace coop