Three fixes for the "most connects simply fail" trap on a SteamOS host
with no physical display (VM testbox, panel-less mini PC):
- restore path: skip the restore-to-physical-panel when no DRM connector
reports a connected display — removing the headless drop-in and
restarting gamescope-session.target on such a box just crash-loops
gamescope and strands every later connect on "no usable compositor".
Keep the headless session (and the takeover state) instead.
- connect path: when no live graphical session exists but the MANAGED
gamescope infra is present (SteamOS gamescope-session / Bazzite
session-plus), route to the gamescope takeover — which rebuilds the
session at the client's mode — instead of failing the connect.
- error delivery: a session-setup failure used to just drop the QUIC
connection, reaching the client as "control stream finished mid-frame"
(indistinguishable from transport trouble). Close with a typed
setup-failed code (0x68, RejectedSetupFailed = -29) carrying the error
text, and give the client handshake/pairing error paths a short grace
for the CONNECTION_CLOSE to beat the stream error it caused.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehler
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