CR-005/D6 fix - a bad CSV row rejects by line number instead of 500ing Postgres

Nick's real location list hit the production import and got 'Internal Server
Error' with no line number - BL-027's class again, three days after the
migration outage: Postgres enforces VARCHAR lengths and refuses control
bytes, SQLite shrugs at both, and the importers were only ever rehearsed on
SQLite. Reproduced both hazards locally (an over-long value and a NUL byte
import cleanly on SQLite; either 500s Postgres wholesale).

Both importers now validate per row, before any INSERT, so every dialect
answers the same way - with the line number and a reason:
- locations: control characters; names over 200; codes over 60; combined
  paths over 200 (checked where the path exists, with read-counts taken
  before the loop so a mid-loop rejection is not counted twice)
- materials: control characters; description/unit/code over 300/20/80

And the client stops lying about it: wp-list-import.js read every response
with r.json(), so a plain-text 500 threw mid-parse and surfaced as 'Could not
reach the server' while the server was answering fine. One tolerant reader
(text -> parse if it parses -> keep status) now serves import, add and patch;
a real error reads 'Import refused - HTTP 500'.

Pins: materials_check +2 (over-long and control-byte rows reject at line,
20/20), locations_check +1 (over-long name rejects at line, 59/59).

Items: CR-005, D6, BL-027 (second instance of its class; the probe-side
dialect guard it proposes is still open).

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

html/wp-list-import.js

@@ -105,6 +105,18 @@
       say(bits.join(''), problem);
     }
 
+    // A 500 answers plain text ("Internal Server Error"), and r.json() on that
+    // throws - which used to land in catch() and read as "could not reach the
+    // server" while the server was answering fine (found 2026-08-23, the
+    // production locations import). Read text, parse if it parses, keep status.
+    function readJson(r) {
+      return r.text().then(function (t) {
+        var j = null;
+        try { j = t ? JSON.parse(t) : null; } catch (e) { /* not JSON: a proxy or 500 page */ }
+        return { ok: r.ok, status: r.status, body: j };
+      });
+    }
+
     function importText(dryRun) {
       var text = (el(p + '-paste') || {}).value || '';
       if (!text.trim()) { say('Paste some rows or choose a CSV file first.', true); return; }
@@ -114,7 +126,7 @@
         method: 'POST', headers: { 'Content-Type': 'application/json', 'Accept': 'application/json' },
         body: JSON.stringify({ text: text, dry_run: !!dryRun }),
       })
-        .then(function (r) { return r.json().then(function (j) { return { ok: r.ok, status: r.status, body: j }; }); })
+        .then(readJson)
         .then(function (res) {
           if (!res.ok) {
             say('⚠ Import refused — ' + esc((res.body && res.body.detail) || ('HTTP ' + res.status)), true);
@@ -142,7 +154,7 @@
         method: 'POST', headers: { 'Content-Type': 'application/json', 'Accept': 'application/json' },
         body: JSON.stringify(read.payload),
       })
-        .then(function (r) { return r.json().then(function (j) { return { ok: r.ok, status: r.status, body: j }; }); })
+        .then(readJson)
         .then(function (res) {
           if (!res.ok) {
             setAddError((res.body && res.body.detail) || ('Could not add it (HTTP ' + res.status + ')'));
@@ -161,7 +173,7 @@
         method: 'PATCH', headers: { 'Content-Type': 'application/json', 'Accept': 'application/json' },
         body: JSON.stringify(patchBody),
       })
-        .then(function (r) { return r.json().then(function (j) { return { ok: r.ok, status: r.status, body: j }; }); })
+        .then(readJson)
         .then(function (res) {
           if (!res.ok) {
             say('⚠ ' + esc((res.body && res.body.detail) || ('HTTP ' + res.status)), true);