data(hanja): a lone consonant is a reading too

Every Korean keyboard's 한자 key answers a lone consonant with the KS X
1001 symbol palette, and has since 한글 워드프로세서: ㅁ for ※ ○ △ ㈜, ㄴ
for the brackets, ㄹ for the units, ㅇ for the circled numbers.  strans
sends that key to the same search as a syllable -- Khanja is Ctrl+H at
strans.c:830, and startsearch seeds the query with whatever ko.c left
pending -- but every one of hanja.dict's 187286 readings is a syllable, so
the popup came up with a query in it and nothing to pick:

	ㅁ: 0 candidates
	ㄴ: 0 candidates
	ㄹ: 0 candidates
	한: 99 candidates 韓 漢 寒 限 閑 恨 旱 汗 翰 邯 罕 悍 澣 閒 瀚

libhangul ships that palette beside the Hanja table already imported here:
data/hanja/mssymbol.txt, same commit, same author, same BSD-3 terms, same
key:value:comment format -- and keyed by the compatibility jamo ko.c
already holds, U+3141 for ㅁ.  So the engine does not change at all; the
same dictlookup on the same trie now finds something:

	ㅁ: 75 candidates ＃ ＆ ＊ ＠ § ※ ☆ ★ ○ ● ◎ ◇ ◆ □ ■ △ ▲ ▽ ▼
	ㄴ: 23 candidates ＂ （ ） ［ ］ ｛ ｝ ‘ ’ “ ” 〔 〕 〈 〉 《 》 「 」
	ㄹ: 94 candidates ＄ ％ ￦ Ｆ ′ ″ ℃ Å ￠ ￡ ￥ ¤ ℉ ‰ € ㎕ ㎖ ㎗ ℓ
	한: 99 candidates 韓 漢 寒 限 閑 恨 旱 汗 翰 邯 罕 悍 澣 閒 瀚

Both scripts widen by one rule -- a syllable reading gives Hanja, a jamo
reading gives a symbol -- and hanja.src regenerates byte for byte as it
was, because upstream's own non-syllable readings are words like ㄱ자집
whose values were never Hanja and still fall out.  985 of mssymbol.txt's
987 rows survive: its ideographic space and its soft hyphen do not, since
a candidate the popup cannot draw is not a candidate, and the row format
separates candidates with a space besides.

The two keyspaces cannot collide -- one is syllables, one is single jamo --
so the 187286 existing rows are unchanged, byte for byte, and 18 rows join
them.  mkhanja takes a source list as mkemoji already does, and keeps each
upstream header, which is why the licence text now appears twice.

89 unit, check-live, check-stress and valgrind all clean.  The five new
assertions were checked by breaking the change five ways: dropping
mssymbol.src from SOURCES, letting issymbol keep a formatting character,
letting a jamo reading keep Hanja, widening isjamo to the vowels, and
making mkhanja reject jamo readings.  Each fails only the tests that exist
for it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

map/libhangul2hanja

@@ -1,7 +1,8 @@
 #!/usr/bin/env python3
-"""Extract Hanja readings from libhangul data."""
+"""Extract Hanja and symbol readings from libhangul data."""
 
 import sys
+import unicodedata
 from pathlib import Path
 
 
@@ -9,12 +10,31 @@ def ishangul(s):
     return s != "" and all(0xAC00 <= ord(c) <= 0xD7A3 for c in s)
 
 
+def isjamo(s):
+    return len(s) == 1 and 0x3131 <= ord(s) <= 0x314E
+
+
 def ishanja(s):
     return s != "" and all(0x3400 <= ord(c) <= 0x4DBF
                            or 0x4E00 <= ord(c) <= 0x9FFF
                            or 0xF900 <= ord(c) <= 0xFAFF for c in s)
 
 
+def issymbol(s):
+    """One rune the popup can draw and a candidate row can carry: not a
+    space, which the row separates candidates with, and not a formatting
+    character, which would leave a blank candidate to pick."""
+    return (len(s) == 1 and not s.isspace() and not ishanja(s)
+            and not unicodedata.category(s).startswith("C"))
+
+
+def keeps(reading, value):
+    """A syllable reading gives Hanja; a jamo reading gives a symbol."""
+    if ishangul(reading):
+        return ishanja(value)
+    return isjamo(reading) and issymbol(value)
+
+
 def extract(src, name):
     comments = []
     entries = []
@@ -32,16 +52,16 @@ def extract(src, name):
         fields = line.split(":")
         if len(fields) != 3:
             raise ValueError(f"{name}:{lineno}: need key:value:comment")
-        reading, hanja, _ = fields
-        if not ishangul(reading) or not ishanja(hanja):
+        reading, value, _ = fields
+        if not keeps(reading, value):
             continue
-        pair = (hanja, reading)
+        pair = (value, reading)
         if pair in seen:
-            raise ValueError(f"{name}:{lineno}: duplicate Hanja reading")
+            raise ValueError(f"{name}:{lineno}: duplicate reading")
         seen.add(pair)
         entries.append(pair)
     if not entries:
-        raise ValueError(f"{name}: no Hanja readings")
+        raise ValueError(f"{name}: no readings")
     return comments, entries
 
 
@@ -63,8 +83,8 @@ def main():
             print(line)
         if comments:
             print()
-        for hanja, reading in entries:
-            print(f"{hanja}\t{reading}")
+        for value, reading in entries:
+            print(f"{value}\t{reading}")
     except (OSError, UnicodeError, ValueError) as error:
         print(error, file=sys.stderr)
         return 1