storkit: create 391_bug_strip_prefix_ci_panics_on_multi_byte_utf_8_characters

.storkit/work/1_backlog/391_bug_strip_prefix_ci_panics_on_multi_byte_utf_8_characters.md

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+---
+name: "strip_prefix_ci panics on multi-byte UTF-8 characters"
+---
+
+# Bug 391: strip_prefix_ci panics on multi-byte UTF-8 characters
+
+## Description
+
+strip_prefix_ci in commands/mod.rs slices text by byte offset using prefix.len(), which panics when the slice boundary falls inside a multi-byte UTF-8 character (e.g. right single quote U+2019, emojis). The function assumes ASCII-safe byte boundaries but real WhatsApp/Matrix messages contain Unicode.
+
+## How to Reproduce
+
+1. Send a message to the bot containing a smart quote or emoji within the first N bytes (where N = bot name length)\n2. e.g. "For now let\u2019s just deal with it" where the bot name prefix check slices at byte 12, inside the 3-byte \u2019 character
+
+## Actual Result
+
+Thread panics: "byte index 12 is not a char boundary; it is inside \u2018\u2019\u2019 (bytes 11..14)"
+
+## Expected Result
+
+The function should safely handle multi-byte UTF-8 without panicking. If the slice boundary isn't a char boundary, the prefix doesn't match — return None.
+
+## Acceptance Criteria
+
+- [ ] strip_prefix_ci does not panic on messages containing multi-byte UTF-8 characters (smart quotes, emojis, CJK, etc.)
+- [ ] Use text.get(..prefix.len()) or text.is_char_boundary() instead of direct indexing
+- [ ] Add test cases for messages with emojis and smart quotes