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>

server/app.py

@@ -2388,6 +2388,24 @@ def parse_location_rows(text: str) -> tuple[list[tuple[int, list[str]]], list[di
             rejected.append({"line": i, "text": line,
                              "reason": "no letters or digits to make a code from"})
             continue
+        # Postgres enforces VARCHAR lengths and refuses NUL/control bytes;
+        # SQLite shrugs at both - which is how ONE bad CSV line 500'd the whole
+        # production import (2026-08-23, BL-027's class again) instead of coming
+        # back as a rejection with its line number. Validate per row, here,
+        # so every dialect answers the same way: with a reason.
+        if any(any(ord(ch) < 32 for ch in p) for p in parts):
+            rejected.append({"line": i, "text": line[:120],
+                             "reason": "contains control characters — re-save the file as plain CSV (UTF-8)"})
+            continue
+        long_p = next((p for p in parts if len(p) > 200), None)
+        if long_p is not None:
+            rejected.append({"line": i, "text": line[:120],
+                             "reason": "a name is longer than 200 characters (%d)" % len(long_p)})
+            continue
+        if any(len(location_slug(p)) > 60 for p in parts):
+            rejected.append({"line": i, "text": line[:120],
+                             "reason": "a code would be longer than 60 characters"})
+            continue
         rows.append((i, parts))
     return rows, rejected
 
@@ -2454,6 +2472,7 @@ def import_locations(project_id: str, body: LocationImportIn,
     require_project_writable(db, user, project_id, "The location list cannot be changed")
 
     rows, rejected = parse_location_rows(body.text)
+    read_total = len(rows) + len(rejected)
 
     existing = {n.path: n for n in db.scalars(
         select(models.LocationNode).where(models.LocationNode.project_id == project_id)
@@ -2468,6 +2487,10 @@ def import_locations(project_id: str, body: LocationImportIn,
     for line_no, parts in rows:
         segs = [location_slug(p) for p in parts]
         full = "/".join(segs)
+        if len(full) > 200:
+            rejected.append({"line": line_no, "text": "/".join(parts)[:120],
+                             "reason": "the combined path is longer than 200 characters"})
+            continue
         if full in seen_in_file:
             duplicates.append({"line": line_no, "path": full, "names": parts,
                                "reason": "already on line %d of this import" % seen_in_file[full]})
@@ -2510,7 +2533,7 @@ def import_locations(project_id: str, body: LocationImportIn,
 
     result = {
         "project_id": project_id, "dry_run": bool(body.dry_run),
-        "read": len(rows) + len(rejected),
+        "read": read_total,
         "created": created, "duplicates": duplicates,
         "reactivated": reactivated, "rejected": rejected,
     }
@@ -3007,6 +3030,18 @@ def parse_material_rows(text: str):
             rejected.append({"line": i, "text": raw.strip()[:120],
                              "reason": "more than three columns - description, unit, code is the whole shape"})
             continue
+        # Same guard as parse_location_rows: reject what Postgres would refuse
+        # (VARCHAR limits, control bytes) with the line number, never a 500.
+        if any(any(ord(ch) < 32 for ch in p) for p in parts):
+            rejected.append({"line": i, "text": raw.strip()[:120],
+                             "reason": "contains control characters - re-save the file as plain CSV (UTF-8)"})
+            continue
+        caps = ((300, "description"), (20, "unit"), (80, "code"))
+        long_col = next((("%s is longer than %d characters (%d)" % (label, cap, len(p)))
+                         for (cap, label), p in zip(caps, parts) if len(p) > cap), None)
+        if long_col:
+            rejected.append({"line": i, "text": raw.strip()[:120], "reason": long_col})
+            continue
         rows.append((i, parts))
     return rows, rejected