New mutating tool, built on the proven journal/rollback foundation. Curated
safe field set only (rejects anything else; never creates a missing field).
Edits are line-number-anchored to the target thread's protocol block via
nc-parse (a shared port/host value in another thread is never touched),
brace-balance-checked before an atomic write, journaled for byte-identical
rollback. Flags: --dry-run (no write), --confirm yes, --site, --netconfig.
Copy-tested: PORT + HOST applied surgically, rollback byte-identical.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
