feat: add collect, config, crypt, plugin packages and fix all lint issues
Add four new infrastructure packages with CLI commands:
- pkg/config: layered configuration (defaults → file → env → flags)
- pkg/crypt: crypto primitives (Argon2id, AES-GCM, ChaCha20, HMAC, checksums)
- pkg/plugin: plugin system with GitHub-based install/update/remove
- pkg/collect: collection subsystem (GitHub, BitcoinTalk, market, papers, excavate)
Fix all golangci-lint issues across the entire codebase (~100 errcheck,
staticcheck SA1012/SA1019/ST1005, unused, ineffassign fixes) so that
`core go qa` passes with 0 issues.
Closes #167, #168, #170, #250, #251, #252, #253, #254, #255, #256
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
8f036518fa