[modem7]

What

Makes a monthly "recreate everything" run possible: ./build-templates.sh all --rebuild --verify.

• VMID_DEFAULT per profile. The examples now have 52000 (base), 52001 (extras) and 52002 (desktop). The builder default no longer gives every profile the same --vmid 52000: with no create args it passes each profile's own VMID_DEFAULT with --auto-vmid (a profile without one still gets 52000, so older configs behave as before). --auto-vmid on its own would start at 100, so --vmid is still passed.
• --rebuild. Replaces each existing template in place, using the create script's --force-overwrite --i-know-what-i-am-doing: the new image is built first and only then is the old template destroyed and recreated. The create script still refuses anything that is not a stopped template. Accepted anywhere before --, like --verify; it cannot be combined with explicit create args, --generate-only or --init.
• Pre-flight, before any build starts. With --rebuild the builder stops if a profile has no valid VMID_DEFAULT, if two profiles share one (the second would overwrite the first), or if a template still has linked clones (qm destroy would fail after the long build). The linked-clone check looks at the local node's /etc/pve/qemu-server.
• --verify with --rebuild. Replacing a template reuses its ID, so the usual "the one new VMID" detection finds nothing. With --rebuild the profile's own ID is verified instead; --keep still works.
• Help text and README updated, including a "Rebuilding in place" section.

Testing

bash -n and shellcheck are clean. Checked against a mocked qm and a stub create script, on a copy with the root check removed: argument parsing and the errors above; default args (including IDs already taken) and --rebuild args; three profiles generated with their own VMID_DEFAULT; duplicate, missing and invalid IDs; linked-clone detection with a fake config folder (base-52001- matched, base-520010- not); --rebuild --verify and --keep; plain --verify unchanged; real --help and --init.

Not run on a real Proxmox host. The create script's real --force-overwrite run, and its loading of VMID_DEFAULT from --config, were checked by reading the code only. Linked clones on other cluster nodes are not detected.