Module write 

The engine’s two writes to a change’s tasks.md: a one-byte tick and the convergence append. Both re-read the file and refuse when it changed since speccoder read it.

Functions

append_convergence

Appends ## N. Convergence with one open task N.k per item, N after the highest numbered group. The file must still hash to expected_file_hash; the old bytes stay an exact prefix. No items → the file is not touched. Returns the new IDs.

tick

Ticks task_id: writes x into its [ ], one byte, nothing else.