feat: debug --sshd flag, auto SSH + nc listener + IP callback

When using `labctl provision debug <target> --sshd`, the rescue
kickstart generates host keys, starts sshd (pw: debug) and nc
listener (port 2323), and reports the IP back to bastion via
/api/progress callback. Fully self-contained, no mounted FS needed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bastion/docs/kickstart-reference.md

@@ -0,0 +1,103 @@
+# Kickstart Reference — Lessons Learned
+
+This documents pitfalls discovered during PXE boot testing. Read before modifying
+the kickstart template (`src/bastion/src/templates/install.ks.ts`).
+
+## Package requirements
+
+### `kernel-modules` is mandatory
+
+`@core` only installs `kernel-modules-core`, which lacks common modules like `vfat`,
+`zram`, and many network/filesystem drivers. Without `kernel-modules`:
+
+- `/boot/efi` (FAT32) cannot mount → `systemd-remount-fs` fails → **root stays
+  read-only** → sshd-keygen can't write host keys → SSH unreachable
+- `zram-generator` fails → can trigger emergency mode
+
+**Always include `kernel-modules` in %packages.** This matches what the real
+labmaster (192.168.8.11) has installed.
+
+Regression introduced in commit `fac14b6` which removed `@server-product`
+(that group pulled in `kernel-modules` via `fedora-release-server`).
+
+### `dosfstools` is needed
+
+Provides `mkfs.vfat` and ensures FAT filesystem support is available. The real
+labmaster has it installed.
+
+### Verify against the real machine
+
+Before changing the package list, SSH to the labmaster and compare:
+```bash
+ssh 192.168.8.11 "rpm -q <package>"
+```
+
+## Anaconda %post execution order
+
+This is critical and not well documented:
+
+1. `%pre` scripts run
+2. Disk partitioning and formatting
+3. Package installation
+4. **Anaconda writes system config (fstab, hostname, etc.)**
+5. `%post` scripts run (in chroot of installed system)
+6. `%post --nochroot` scripts run
+7. **Anaconda MAY overwrite fstab again after %post scripts**
+
+**Consequence:** You cannot reliably modify `/etc/fstab` from `%post` or
+`%post --nochroot`. Anaconda overwrites it. Tested and confirmed — both
+`sed` in %post and %post --nochroot had no effect on the final fstab.
+
+What DOES work from %post:
+- Writing files to `/etc/` (systemd units, config files, SSH keys)
+- Enabling/disabling systemd services
+- Installing additional packages
+- Running `systemctl enable/mask`
+
+What does NOT work from %post:
+- Modifying `/etc/fstab` (Anaconda overwrites it)
+- `--fsoptions` on `part /boot/efi` (Anaconda ignores it for EFI partitions)
+
+## UEFI / EFI partition
+
+- Anaconda always creates an EFI System Partition for UEFI installs
+- The EFI partition is FAT32 — requires `vfat` kernel module to mount
+- If `/boot/efi` fails to mount, `systemd-remount-fs` fails, which leaves
+  root as read-only. This cascades to break ALL services that need to write
+- The EFI partition is used by firmware directly for bootloader — the OS
+  doesn't strictly need it mounted, but Anaconda adds it to fstab
+
+## VM-specific issues (libvirt/QEMU/OVMF)
+
+### iPXE exit behavior
+- `exit` (no args) returns EFI_SUCCESS → OVMF retries PXE, never reaches disk
+- `exit 1` returns EFI_ABORTED → OVMF moves to next boot device (disk)
+- VM boot order needs both `network` and `hd`: `--boot=uefi,network,hd`
+
+### nftables
+- libvirt creates reject rules for NAT networks in table `ip libvirt_network`
+  (NOT `inet libvirt` — this wrong table name cost hours of debugging)
+- These rules block new host→VM connections (SSH)
+- Rules are recreated on every `virsh start` — must delete after each VM restart
+- Chains: `guest_input` and `guest_output`
+
+### Serial console
+- VM serial port: `--serial=tcp,host=127.0.0.1:4555,mode=bind,protocol=telnet`
+- Use `virsh console <vm-name>` for interactive access (handles telnet protocol)
+- Raw `socat` works for reading but pagers/readline break interactive use
+- Add `console=ttyS0,115200n8` to kernel args for boot output on serial
+
+### SELinux on labmaster
+- Set to **permissive** — this is for k3s/kubernetes, NOT because SSH needs it
+- SSH works fine with SELinux enforcing on a properly installed Fedora system
+- The `ld.so.cache` AVC denials seen during debugging were caused by the
+  read-only root filesystem, not by SELinux policy
+
+## Testing checklist
+
+Before merging kickstart changes:
+1. Check the real labmaster has the same packages: `ssh 192.168.8.11 "rpm -q <pkg>"`
+2. Run the PXE integration test: `sudo pnpm run test:integration:pxe`
+3. Verify via serial console (root / `lab-root-pw`) if SSH fails
+4. Check `mount | grep " / "` — must show `rw`, not `ro`
+5. Check `systemctl --failed` — no critical failures