dev: promote DOSBox-X and remove QEMU support

TODO.md

@@ -1,27 +0,0 @@
-# TODO
-
-## Done
-
-- [x] Add a non-reboot abort path for a hung DOS command: inject `Ctrl+C` through
-      QEMU's monitor and wait for the agent to recover.
-- [x] Apply a configurable timeout to `exec` and invoke the non-reboot abort path
-      on timeout.
-- [x] Expose `abort` for an immediate user-requested command interruption.
-
-The three above were first built for the COM1 serial agent, lost in the rewrite
-to the resident TCP agent, and rebuilt on the QEMU monitor in `ferro-vm exec`.
-The TCP version supervises with guest disk liveness (`info blockstats`) rather
-than a fixed stopwatch, so a slow compile is no longer mistaken for a hang.
-
-## Open
-
-- [ ] Consider `BREAK=ON` in `C:\FDCONFIG.SYS`. Ctrl+C only takes effect at a DOS
-      break check, and with the FreeDOS default of `BREAK=OFF` a compute-bound
-      child whose output is redirected to a file may never reach one, so `abort`
-      cannot always stop it. `BREAK=ON` checks on every DOS call and makes the
-      abort reliable, at a small cost to every DOS call. Needs a VM reboot; back
-      up `FDCONFIG.SYS` first.
-- [ ] `TCPAGENT.EXE` connects from a fixed source port (`LOCAL_PORT 2058`). After
-      the host end closes, a reconnect reuses the same 4-tuple and can flap until
-      the old state ages out. Observed as a ~10s connect/disconnect cycle after
-      the daemon is killed mid-connection.