v0.2.6

Added

• aegis doctor — SDK health diagnostics: config, keys, canister, spill, API key status
• aegis init --quickstart — non-interactive setup with Ed25519 defaults (no prompts)
• aegis register-key — register a new API key with PoP from CLI
• aegis revoke — revoke an API key with confirmation prompt
• Error classes — AegisAuthError, AegisConfigError, AegisTransportError with human-readable messages
• translate_error() — maps canister error strings to actionable hints
• 30 new tests

Changed

• AegisError and CanisterError moved to errors.py (backward-compatible re-export from transport.py)