Telegram Bot API requires command names to contain only lowercase a-z,
digits 0-9, and underscores. Skill/plugin names containing characters
like +, /, @, or . caused set_my_commands to fail with
Bot_command_invalid.
Two-layer fix:
- scan_skill_commands(): strip non-alphanumeric/non-hyphen chars from
cmd_key at source, collapse consecutive hyphens, trim edges, skip
names that sanitize to empty string
- _sanitize_telegram_name(): centralized helper used by all 3 Telegram
name generation sites (core commands, plugin commands, skill commands)
with empty-name guard at each call site
Closes#5534
214e60c951