fix: reject '.' and leading '-' in party names

tmux session_check_name() silently rewrites '.' to '_', so a dotted
party name desyncs from its tmux session and every -t lookup fails
(verified on tmux 3.3a through 3.6b). Leading-dash names can never be
addressed through the CLI parsers.

party

@@ -65,30 +65,32 @@ EOF
 # Helpers
 # =======
 
-# Validate a party name. Accepts [A-Za-z0-9._-]{1,63}. Reject empty,
-# paths, shell metas, and overlong names: the name lands in a file
-# path component, a tmux session name, and shell command lines.
+# Validate a party name. Accepts [A-Za-z0-9_-]{1,63}, not starting with
+# '-'. Reject empty, paths, shell metas, and overlong names: the name
+# lands in a file path component, a tmux session name, and shell
+# command lines. Dots are rejected because tmux's session_check_name()
+# silently rewrites '.' (and ':') to '_', which would desync the party
+# name from its tmux session and break every later `-t <name>` target.
+# Leading '-' is rejected because every subcommand parser would eat the
+# name as a flag, so such a party could never be addressed.
 validate_party_name() {
     name="$1"
     case "$name" in
         '' )  echo "party: name must not be empty" >&2; return 2 ;;
     esac
-    # Length cap: 63 keeps the full /tmp/party-${USER}-${name} comfortably
-    # below the 108-char sun_path limit for typical USERs.
+    # Length cap: 63 keeps the full socket path comfortably below the
+    # 108-char sun_path limit for typical USERs.
     if [ "${#name}" -gt 63 ]; then
         echo "party: name '$name' too long (max 63 chars)" >&2
         return 2
     fi
     case "$name" in
-        *[!A-Za-z0-9._-]* )
-            echo "party: name '$name' has invalid characters" >&2
-            echo "       allowed: letters, digits, '.', '_', '-'" >&2
+        -* )
+            echo "party: name must not start with '-'" >&2
             return 2 ;;
-    esac
-    # Reject ".", "..", and any leading-dot variant we don't want.
-    case "$name" in
-        .|.. )
-            echo "party: name '$name' is reserved" >&2
+        *[!A-Za-z0-9_-]* )
+            echo "party: name '$name' has invalid characters" >&2
+            echo "       allowed: letters, digits, '_', '-'" >&2
             return 2 ;;
     esac
     return 0
@@ -237,10 +239,13 @@ roster_read() {
     [ -n "$RR_PARTY_NAME" ] || return 1
 
     # Pattern parity with cmd_host. The basename glob (party-*:*.d) is
-    # permissive, names like '.' (basename party-USER:..d) or 'a b'
-    # match the glob but validate_party_name rejects them. Run the
-    # canonical validator so the invariant cmd_host enforces on write
-    # is also checked on read.
+    # permissive — names like 'a b' or 'my.party' match the glob but
+    # validate_party_name rejects them (dots are banned: tmux rewrites
+    # them in session names). Run the canonical validator so the
+    # invariant cmd_host enforces on write is also checked on read.
+    # Side effect: pre-existing dotted-party dirs from older builds
+    # become undiscoverable, which is the pre-release migration policy
+    # (README §Status).
     validate_party_name "$RR_PARTY_NAME" 2>/dev/null || return 1
 
     # Both the dir and its sock must be owned by the user named in the