Station flow: ID first, EAN optional, re-measure by ID

Every run opens with the freshly allocated L#### and then asks for
the EAN, which Enter skips. Typing an existing ID re-measures that
lamp with all identification and rated values pre-filled, which also
rewrites old bundles in the current metrics format. Unused IDs are
never burned since numbering derives from written bundles.

README.md

@@ -97,9 +97,13 @@ end to end. Every lamp gets an internal ID (L0001, L0002, ...) as primary key;
 the EAN barcode is optional metadata, so one barcode can cover daylight/warm
 white variants (distinct IDs + variant field) and unbranded lamps work too.
 
-Per lamp: scan the box (or 'n' for no barcode), the EAN is checksum-validated
-and resolved to manufacturer/model (previously measured lamps, local cache,
-then upcitemdb.com; GS1-restricted 20-29 barcodes are flagged as
+Every run opens with a freshly allocated ID (the ID only becomes real once a
+bundle is written, so aborting never burns a number). Then: scan the box's EAN
+(optional, Enter skips it), or type an existing ID like L0004 to re-measure
+that lamp with everything pre-filled, which also rewrites its bundle in the
+current metrics format. Scanned EANs are checksum-validated and resolved to
+manufacturer/model (previously measured lamps, local cache, then
+upcitemdb.com; GS1-restricted 20-29 barcodes are flagged as
 retailer-internal), lamps already measured under the same EAN are offered for
 re-measurement, you confirm the identification and type the ADVERTISED values
 from the packaging (flux, CCT, power, CRI, lifetime, equivalent W -> stored