The corpus is uniform — every PDF is <index>.pdf flat in the import
dir — so resolve a document's PDF with an O(1) importDir.resolve(index
+ ".pdf") lookup instead of a recursive directory walk over the file
column. The index is validated against a strict catalog pattern
(1–4 Latin letters incl. umlauts, hyphen(s), digits, optional x) plus
the ported separator/dot/dotdot/null/slash-homoglyph/absolute-path
guards, and the resolved canonical path is asserted to stay inside the
import dir as defense-in-depth. The %PDF magic-byte check still gates
upload; status UPLOADED/PLACEHOLDER and the index→originalFilename
upsert key are unchanged. The file column and findFileRecursive walk
are gone, and the security regression tests now assert a malicious or
garbage index is rejected and a valid index resolves to exactly
importDir/<index>.pdf within containment.
Closes#686Closes#676
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>