Answer product-owner round 1: name the field exchange, and say in plain words what phone-exchange draws

CHANGELOG.md

@@ -90,8 +90,9 @@ replacement, and each removed path, column or flag.
   and carries the same three. `person.prefix` is null where a person has no title,
   where it used to be an empty string, so `--format sql` writes `NULL` and a `string`
   struct field reading it becomes `*string`.
-- `en_US.phone-exchange` draws a central office code NANPA can assign: `200` to `999`,
-  never `N11`, `555`, `950`, `958`, `959` or `976`. `en_US.phone` draws its `exch` from it.
+- `en_US.phone-exchange` draws the three digits after a US area code, as NANPA assigns
+  them: `200` to `999`, never `211` to `911` ending in `11`, nor `555`, `950`, `958`,
+  `959` or `976`. `en_US.phone` draws its `exchange` from it.
 - `ErrNoColumns` is exported, so a caller can tell the one record fence a path can
   answer from the rest.
 - An error names a spelling that runs: a layout is named single-quoted and free of

README.md

@@ -161,16 +161,17 @@ which binds a [name](#names), nor be `-`, which a struct tag reserves; dot-prefi
 
 Each locale carries `address`, `color`, `company`, `date`, `email`, `first-name`,
 `ip`, `last-name`, `person`, `phone`, `price`, `sentence`, `sex`, `time`, `url`,
-`username`, `version` and `word`, formatted per locale; `sv_SE` adds
-`personnummer` and `samordningsnummer`, `en_US` adds `ssn`, `itin` and `phone-exchange`. `misc`
-carries `car`, `coordinate`, `creditcard` (Luhn-valid), `currency` (ISO 4217),
-`datetime` (RFC 3339), `emoji`, `httpmethod`, `httpstatus`, `language` (ISO 639-1,
-with its 639-2/T code), `loglevel` (syslog severity), `mac`, `mimetype`, `objectid`,
-`port`, `protocol`, `territory` (ISO 3166-1), `timezone` (IANA), `tld` (IANA root
-zone), `useragent` and `uuid` (v4). Many carry sub-fields — `misc.currency.symbol`,
-`misc.territory.alpha2`, `misc.httpstatus.code` — which `--list` shows. `car`,
-`currency`, `httpmethod`, `httpstatus`, `language`, `loglevel`, `mimetype`, `port`,
-`protocol`, `territory`, `timezone`, `tld` and `useragent` are [tables](#table), so
+`username`, `version` and `word`, formatted per locale; `sv_SE` adds `personnummer`
+and `samordningsnummer`, `en_US` adds `ssn`, `itin` and `phone-exchange` (the three
+digits after the area code). `misc` carries `car`, `coordinate`, `creditcard`
+(Luhn-valid), `currency` (ISO 4217), `datetime` (RFC 3339), `emoji`, `httpmethod`,
+`httpstatus`, `language` (ISO 639-1, with its 639-2/T code), `loglevel` (syslog
+severity), `mac`, `mimetype`, `objectid`, `port`, `protocol`, `territory` (ISO
+3166-1), `timezone` (IANA), `tld` (IANA root zone), `useragent` and `uuid` (v4). Many
+carry sub-fields — `misc.currency.symbol`, `misc.territory.alpha2`,
+`misc.httpstatus.code` — which `--list` shows. `car`, `currency`, `httpmethod`,
+`httpstatus`, `language`, `loglevel`, `mimetype`, `port`, `protocol`, `territory`,
+`timezone`, `tld` and `useragent` are [tables](#table), so
 `misc.territory[SE].capital` and `misc.currency[Euro].symbol` select a row; `car` and
 `useragent` carry no key or name, so they are drawn from rather than selected in.
 

data/en_US/phone.json

@@ -1,15 +1,15 @@
 [
   {
-    "format": "({area}) {exch}-{line}",
+    "format": "({area}) {exchange}-{line}",
     "weight": 2,
     "area": ["202", "212", "213", "305", "312", "404", "415", "469", "503", "512", "602", "617", "646", "702", "718", "720", "737", "773", "786", "808", "917"],
-    "exch": "{.phone-exchange}",
+    "exchange": "{.phone-exchange}",
     "line": "{digits(4)}"
   },
   {
-    "format": "{area}-{exch}-{line}",
+    "format": "{area}-{exchange}-{line}",
     "area": ["202", "212", "213", "305", "312", "404", "415", "469", "503", "512", "602", "617", "646", "702", "718", "720", "737", "773", "786", "808", "917"],
-    "exch": "{.phone-exchange}",
+    "exchange": "{.phone-exchange}",
     "line": "{digits(4)}"
   }
 ]

shippedindex.go

@@ -13,7 +13,7 @@ var shippedIndex = map[string]shippedEntry{
 	"en_US.itin":              {paths: []string{"", "area", "group", "serial"}},
 	"en_US.last-name":         {paths: []string{"", "count", "name"}},
 	"en_US.person":            {paths: []string{"", "first", "last", "prefix", "sex"}},
-	"en_US.phone":             {paths: []string{"", "area", "exch", "line"}},
+	"en_US.phone":             {paths: []string{"", "area", "exchange", "line"}},
 	"en_US.phone-exchange":    {paths: []string{""}},
 	"en_US.price":             {paths: []string{"", "amt", "cents"}},
 	"en_US.sentence":          {paths: []string{"", "adj", "noun", "prep", "verb"}},