Container nix invocations hard-failed whenever the remote builder
muede-pc2 was unreachable, while the identical build on the host
succeeded. Both go through the same host nix-daemon, so the difference
looked impossible.
The cause is that `fallback` is a client-side option: the nix client
transmits it to the daemon per connection (`tryFallback` in setOptions),
so the caller decides whether a failed remote dispatch may degrade to a
local build — even when the build itself runs on the host daemon under
NIX_REMOTE=daemon. Only genuinely daemon-side settings such as
`builders` are inherited from the host. The containers never set
`fallback`, so they took nix's default of false.
Set it in the agent-container base module and in the CI container, and
correct the hive-ci comment that claimed fallback was inherited from
the host daemon along with buildMachines and max-jobs.
Verified in an agent container: `nix fmt` fails outright on the remote
store's connection reset, while the same command with fallback enabled
reports the same connection error and then builds locally and succeeds.
New crate hive-screen-mcp: a stdio MCP bridge activated automatically
when an agent has hyperhive.gui.enable = true. Provides five tools:
- screenshot — grim → saves PNG, returns path for Read tool
- type_text — wtype → Unicode text input (no daemon)
- key_press — ydotool key → combos like ctrl+c, super+l
- mouse_move — ydotool mousemove --absolute
- mouse_click — ydotool click, optionally with prior move
New nix/agent-modules/screen.nix: wires the MCP bridge into
extraMcpServers.screen; adds grim + wtype to systemPackages. Adds
hyperhive.gui.screenInput option (default false) which enables the
ydotoold daemon + ydotool for mouse/keyboard injection via /dev/uinput.
screenshot and type_text work without screenInput. key_press,
mouse_move, and mouse_click return a ydotool error until ydotoold is
running and /dev/uinput is accessible in the container.
