Add 740 total tests (up from ~200) covering:
- Compile-time interface compliance for all providers
- GetCapabilities assertions for every provider
- Parse function edge cases: empty, malformed, single-entry, multi-entry
- apt: extract inline parse logic into testable functions (parsePolicyCandidate,
parseUpgradeSimulation, parseHoldList, parseOwner, parseSourcesLine)
- dnf/rpm: edge cases for both dnf4 and dnf5 parsers, normalize/parseArch
- pacman/aur: parseUpgrades, parseGroupPkgSet, capabilities
- apk: parseUpgradeSimulation, parseListLine, SupportsDryRun
- flatpak/snap: semverCmp, stripNonNumeric edge cases
- pkg/ports: all parse functions with thorough edge cases
Every provider now has:
- Interface compliance checks (what it implements AND what it doesn't)
- Capabilities test via snack.GetCapabilities()
- Parse function unit tests with table-driven edge cases
Implements the snack.Manager interface for Alpine Linux's apk-tools:
- Install, Remove, Purge, Upgrade, Update operations
- List installed, Search, Info, IsInstalled, Version queries
- Output parsing for apk list, search, and info formats
- Linux-only implementation with build-tag stubs for other platforms
- Options support: WithSudo, WithDryRun, WithRoot
- Tests for all output parsing functions
