Fix minor issues and store state for private_networking atomically

[Siddharth More (siddimore)]

Summary

Fixes six bugs across the bootstrap and privatenetworking packages covering state corruption, silent error swallowing, a production panic, and log stream contamination.

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Changes

private_networking.go: Non-atomic state write + error not propagated

Both the destroy and apply paths used os.WriteFile to persist Terraform state a truncate-then-write that corrupts the state file if the process crashes mid-write.

Fix: Exported PersistTerraformState from state_persistence.go.

Note: privatenetworking is described as a temporary stopgap. If it's being retired soon, this fix may be unnecessary.

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private_networking.go: All os.Stat errors treated as "file not found"

os.Stat errors on the state file were silently treated as "no state file exists", including permission errors and I/O errors. This caused Terraform to start from blank state, diverging from the real infrastructure state.

Fix: Added errors.Is(err, os.ErrNotExist) guard

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gcp.go: panic(err) reachable from user input

pflag's Bool type rejects empty string, so if a user entered an invalid boolean value would fail and trigger a panic. This crashed the CLI with a stack trace instead of a graceful error.

Fix: Capture the error in a visitErr closure variable, skip remaining flags, and return it after VisitAll completes. Added a comment explaining why the "impossible" case is actually reachable.

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state_migration_backup.go: Read error swallowed during backup verification

os.ReadFile and bytes.Equal errors were collapsed into a single opaque "could not be verified" message with no underlying cause.

Fix: Separated into two distinct checks

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bootstrap.go: Dead variable and silent MarshalJSON error

json.Unmarshal populated variable m that was never used (raw bytes were printed directly). MarshalJSON error was _-discarded — if it failed.

Fix: Removed the json.Unmarshal

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logger.go: Structured logs written to stdout instead of stderr

aws scopes add writes a parseable scope-ref to cmd.OutOrStdout() for machine consumption. With logs on stdout, any info-level log output contaminated that stream when piping or redirecting.

Fix: Changed os.Stdout → os.Stderr