feat: cosmology CLI env vars, cosmology-compat rename, bitcoin-first networks

[pyramation]

Summary

Every env var the cosmology CLI read now works in dcrypt, restoring script compatibility that the new flags-only design had broken:

Variable	Used by
MNEMONIC	wallet address / wallet validate
SALT, ENCRYPTED_SALT	cosmology decrypt / upgrade
KEYCHAIN_ACCOUNT	keychain namespace → keychain-<account>.json (default dcrypt → keychain.json)
DCRYPT_PASSPHRASE	any passphrase prompt (new, for unattended runs)

Each also has a DCRYPT_-prefixed alias (utils/env.ts is the single resolution point). Precedence everywhere: explicit flag → environment → stdin → interactive prompt; secrets in argv remain rejected.

@decryption/legacy → @decryption/cosmology-compat (nothing was published under the old name). The CLI command is now dcrypt cosmology decrypt|upgrade, with dcrypt legacy kept as an alias so existing invocations keep working.

Bitcoin is the default network, Ethereum second: NETWORKS reordered (bitcoin, ethereum, then cosmos-family), DEFAULT_NETWORK = 'bitcoin' exported and used by createWallet and dcrypt wallet (was cosmoshub); the desktop wallet tool's selector now lists all ten networks in the same order and defaults to bitcoin.

New tests: SALT/MNEMONIC/DCRYPT_PASSPHRASE/KEYCHAIN_ACCOUNT paths, the legacy alias, and the bitcoin default (bc1 address).

Link to Devin session: https://app.devin.ai/sessions/04636534e07048089ffb6b78142e12cd
Requested by: @pyramation

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment, CI, and merge conflict monitoring