fix: skip restart request for named sessions on self-handoff

[quad341]

Summary

• Fixes gc handoff: self-handoff crashes human-attended (named) sessions on PreCompact #744: the default PreCompact hook runs gc handoff "context cycle", which called setRestartRequested unconditionally. Named (human-attended) sessions like the mayor are started by the user, and the controller cannot respawn them — so every context compaction killed Claude Code to the user's shell.
• Before requesting a restart, doHandoff now looks up the open session bead for the current session and skips both the tmux and bead restart flags when the bead is a configured named session. Mail is still sent — context preservation was the whole point.

Why

The fix the issue describes — "check whether the current session is a named session, if so skip the restart and return after sending the mail" — matches what I did. isNamedSessionBead (the existing helper from cmd/gc/named_sessions.go) returns true when Metadata["configured_named_session"] == "true". A new local helper sessionIsNamed(store, sessionName) scans open session beads by the existing gc:session label and returns true only for a positive match, so pool sessions (which either have no bead at all or a non-named one) stay on the old restart path.

Test plan

• New regression test: TestDoHandoff_Regression744_NamedSessionSkipsRestart in cmd/gc/cmd_handoff_test.go seeds a named-session bead and asserts mail is created, dops.restartRequested is NOT set, bead restart_requested is NOT set, and stdout does not promise a restart. Fails on main, passes after the fix.
• Sibling tests pass: go test ./cmd/gc/ -run 'TestHandoff|TestDoHandoff' — the pre-existing TestHandoffSuccess / TestHandoffWithMessage / TestHandoffRemote* all continue to pass.
• go vet ./cmd/gc/ clean.
• go build ./cmd/gc/ clean.

🤖 Generated with Claude Code

[julianknutsen]

Adopted Review Summary

I adopted this PR and pushed a maintainer fixup on top of the contributor commit while preserving contributor authorship.

What changed during adoption

• Rebasing brought the branch onto current main.
• gc handoff now returns instead of blocking when a named on-demand session skips restart.
• The restartability check now distinguishes controller-managed always named sessions from on-demand named sessions.
• gc handoff --target skips killing on-demand named targets that the controller cannot restart.
• gc runtime request-restart now uses the same on-demand named-session guard.
• Skip paths clear stale restart metadata and fail closed if stale cleanup cannot be completed.
• CLI help/reference docs were updated for the new semantics.

Review result

Triple-model review validated the core #744 fix: handoff mail is still created, but on-demand named sessions no longer request controller restart or emit a misleading drain event. A follow-up review finding about swallowed stale-cleanup errors was fixed before push.

Remaining broader policy questions are not blockers for this scoped bug fix: whether gc session reset should also refuse or warn for on-demand named sessions, and whether the reconciler should enforce named-session restartability as a defense-in-depth invariant.

Local verification

• go test ./cmd/gc -run 'TestHandoff|TestDoHandoff|TestRuntimeRequestRestart|TestRequestRestartAcceptsNoArgs|TestDoRuntimeRequestRestart|TestReconcileSessionBeads_.*Restart|TestReconcileAndWake_Restart' -count=1
• go vet ./cmd/gc
• go test ./test/docsync -count=1