Tracking fws U6: apply_patch publishes through the guard #2021

What this unit delivers: the apply_patch tool publishes through the guard; a move carries the source's completeness to its destination instead of claiming completeness for lines the model never read; a partial-source move onto an already-observed destination is rejected before any state changes. It also rolls back the parent directories saveDirectly created when the guard refuses the publish.

Why it matters: patch hunks are the easiest way to "write" a file the model never fully read; routing them through the guard closes that hole.

Implemented by: PR #1915 (branch fws/u6-apply-patch-wiring).

Acceptance:

• apply_patch publishes via guardedWrite; an unobserved overwrite and a stale version token are refused with the standard remediation.
• A move inherits the source's complete flag; a partial-source move onto an observed destination is refused pre-state-change.
• saveDirectly removes the directories it created (innermost-first, rmdir refuses a populated directory) and rethrows the original error.

Part of the file-write-safety epic #1375, landed as a nine-PR chain tracked on #1991. Merge order: U1 -> U2 -> U3 -> U4 -> U5 -> U8 -> U6 -> U7 -> U9.