fleetd #480: ignore the handover file, and note the absolute-path guarantee in the handover skill

The lead rollover handover file now lives inside the workspace, at the relative
path fleetd.yaml's leadRollover.handoverPath names. It is a snapshot of one
moment's live state, so it must never enter git history.

The handover skill also now says the handoverPath fleetd hands back is always
absolute, even when the configured value is relative — a lead that resolves it
itself can pick a different file from the one the daemon checks.

.claude/skills/handover/SKILL.md

@@ -135,6 +135,12 @@ refused.**
 
 1. **`fleet_handover{action: "open", reason: "<why now>"}`.** It returns a `token` and the
    `handoverPath` you must write to. Nothing has happened to your pane yet.
+
+   **Write to exactly that path, and do not resolve it yourself.** It is always absolute, even when
+   the operator configured a relative `handoverPath`: fleetd resolves a relative one against your
+   own workspace before it hands it to you. The daemon and your pane can run in different
+   directories, so a path you resolve yourself can point at a different file from the one the daemon
+   will check.
 2. **Write the handover file at that path**, following sections 1–10 above.
 3. **Ask the operator, then `fleet_handover{action: "confirm", token, operatorConfirmed: true}`.**
 

.gitignore

@@ -19,3 +19,9 @@
 fleetd.out
 fleetd/fleetd.out
 logs/
+
+# fleetd #480: the lead rollover handover file. `leadRollover.handoverPath` points here, and the
+# outgoing lead rewrites it on every rollover. It is a snapshot of one moment's live state —
+# unpushed branches, running builds, open questions — so it is stale the moment it is written and
+# has no business in git history.
+.handover/