spam-ascii: fuzzy-match helper for /spam alias

New .local/bin/spam-ascii POSIX shell script: resolves a pattern to
a file in ~/ascii with this order:

  1. exact filename match
  2. exact name + common ASCII-art extension (.txt/.ans/.asc)
  3. first case-insensitive substring match (sorted alphabetically)

Non-zero exit + stderr-ish error if nothing matches, so /spam
prints 'no match in ~/ascii for: <pattern>' instead of spewing
a missing-file error.

Rewire the irssi /spam alias to call the script instead of
hardcoding 'cat ~/ascii/$0'. Now:

  /spam mario     -> matches ~/ascii/mario.txt or ~/ascii/Mario_art.ans
  /spam MARIO     -> case-insensitive
  /spam nothere   -> 'no match in ~/ascii for: nothere'

.local/bin/spam-ascii

@@ -0,0 +1,46 @@
+#!/bin/sh
+#
+# spam-ascii — cat a file from ~/ascii given a partial/fuzzy name.
+#
+# Resolution order:
+#   1. exact filename match: ~/ascii/<pattern>
+#   2. exact name + common extension: <pattern>.txt, .ans, .asc
+#   3. first case-insensitive *substring* match (sorted alphabetically)
+#
+# If nothing matches, prints a friendly error to stdout and exits non-zero.
+# Used by the irssi /spam alias, which pipes our stdout as channel messages.
+
+set -eu
+
+pattern=${1:-}
+if [ -z "$pattern" ]; then
+    echo "usage: spam-ascii <pattern>"
+    exit 1
+fi
+
+dir="$HOME/ascii"
+
+# 1 + 2. Try exact name, then exact + common ASCII-art extensions.
+for candidate in \
+        "$dir/$pattern" \
+        "$dir/$pattern.txt" \
+        "$dir/$pattern.ans" \
+        "$dir/$pattern.asc"; do
+    if [ -f "$candidate" ]; then
+        cat "$candidate"
+        exit 0
+    fi
+done
+
+# 3. First case-insensitive substring match.
+match=$(find "$dir" -maxdepth 1 -type f -iname "*$pattern*" 2>/dev/null \
+        | sort \
+        | head -n1)
+
+if [ -n "$match" ]; then
+    cat "$match"
+    exit 0
+fi
+
+echo "no match in ~/ascii for: $pattern"
+exit 1