Telegram Bot API requires command names to be 1-32 characters. Plugin
and skill names that exceed this limit now get truncated. If truncation
creates a collision (with core commands, other plugins, or other skills),
the name is shortened to 31 chars and a digit 0-9 is appended.
Adds _clamp_telegram_names() helper used for both plugin and skill
entries in telegram_menu_commands(). Core CommandDef commands are tracked
as reserved names so truncated plugin/skill names never shadow them.
Addresses the fix from PR #4191 (sroecker) with collision-safe truncation.
Tests: 9 new tests covering truncation, digit suffixes, exhaustion, dedup.
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