[Olorunshogo]

PR description

Description

key generate --entropy only matched 12; every other value was silently coerced to a 24-word mnemonic. BIP39 and bdk_wallet support 12, 15, 18, 21 and 24 words.

--entropy now parses into a MnemonicWordCount ValueEnum limited to those five values, so invalid input is rejected at parse time and --help lists the options. The flag name, -e, WORD_COUNT env var and default of 12 are unchanged.

Fixes #362

--entropy	Before	After
12 / default	12 words	12 words
15 / 18 / 21	24 words	15 / 18 / 21 words
24	24 words	24 words
0 / 13 / 999	24 words	error listing valid values

Notes to reviewers

• WordCount derives no traits (no Clone), so clap can't parse into it directly. MnemonicWordCount mirrors it with a From impl, following the ScriptType pattern used by compile --type.
• Behavior change: values other than 12 that previously produced 24 words now error. Noted in the CHANGELOG.

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

Bugfixes:

• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[emma31-dev]

Looks good to me. I'll test it later.