v0.1.8: Fix VM stop failure and session-leader PID identity

- Fix stop failing with "PID identity not verified" for session-leader VM children
- proc_pidinfo returns zeroed struct for setsid() children on macOS; treat as unavailable
- Allow stop_process_fast when agent acknowledged shutdown over vsock
- Fix license to Apache-2.0 across all workspace crates

v0.1.7: Fix interactive exec crash and packed binary startup race

- Fix EAGAIN (os error 35) crashing interactive sessions during large output
- Fix packed binary "failed to fill whole buffer" by verifying agent readiness with ping
- Detect POLLHUP/POLLERR on vsock to report "connection to VM lost" cleanly
- Fix infinite recursion in build.rs link_krun() on Linux

v0.1.6: Eliminate smolvm-stub, main binary as packed runtime

- Removed smolvm-stub crate (~2100 lines); main smolvm binary now serves as both CLI and packed runtime
- Auto-detection at startup: Mach-O section, sidecar, or embedded mode
- Weak-link libkrun on macOS so packed binaries can start without it
- Added cs.disable-library-validation entitlement for packed binary code signing
- New run-packed subcommand for explicit .smolmachine execution