docs: Herdr boot persistence applied and verified

/boot/config/go now restores /root/.local/bin/herdr-core from
/boot/config/herdr/herdr-core at boot, with install -m 755 since /boot is
FAT32 and carries no execute bit.

Verified without rebooting: deleted the binary, ran the go line by hand, got
it back executable and reporting hc 0.1.17, with Herdr still connected.
sh -n /boot/config/go parses cleanly. The go script was backed up to
go.bak-20261103-203916 before editing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/CHANGELOG.md

@@ -16,7 +16,7 @@
 ### Tooling: Unraid registered as a Herdr (hc) machine
 - **[SERVICE]** Unraid added to Herdr as the machine `unraid` (`hc` 0.1.17 on the remote). `herdr-core machine add` had been failing with `core did not start within 5 s`: `hc` puts its core socket under `XDG_RUNTIME_DIR`, which on Unraid is `/run/user/0` — a directory elogind creates and destroys per login session, so the socket disappeared the moment the session that started the core ended. The core kept running with an unlinked socket, and `core.log` stayed empty because the failure is client side.
 - **[SERVICE]** Fixed from the Mac only, via `~/.local/bin/herdr-via-unraid`, a `--via` transport that exports `XDG_RUNTIME_DIR=/var/run/herdr-rt` on every connection. Nothing on the server was changed. Uses key auth on 192.168.10.20:422 rather than Tailscale SSH, because `--via` needs a transport that asks nothing and the default tailnet ACL `check` would demand periodic browser re-auth.
-- **[SERVICE]** Reboot caveat: `/` is rootfs (RAM) and `/run` is tmpfs on Unraid, so `/root/.local/bin/herdr-core` is lost at every boot and needs `herdr-core machine update` to restore. A `/boot/config/go` entry to restore it automatically is written up but **not applied**. Detail in `docs/14-HERDR-REMOTE-MACHINES.md`.
+- **[SERVICE]** Reboot caveat: `/` is rootfs (RAM) and `/run` is tmpfs on Unraid, so `/root/.local/bin/herdr-core` is lost at every boot and needs `herdr-core machine update` to restore. A `/boot/config/go` entry now restores it at boot from `/boot/config/herdr/herdr-core` (`install -m 755`, because /boot is FAT32 and carries no execute bit). Applied 2026-11-03, with the go script backed up to `go.bak-20261103-203916` and verified by deleting the binary and running the line by hand. Detail in `docs/14-HERDR-REMOTE-MACHINES.md`.
 - Corrected the 192.168.31.0/24 note: the shim was created in the go script for a Pi-hole at 192.168.31.4, which AdGuard replaced. No such container exists and the address is silent.
 
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