build-docs.sh: find-error check can never fire (PIPESTATUS cannot see inside process substitution)

The find-error check in build-docs.sh is structurally dead code — real find failures are always misreported as "no files found".

The defect

In the default-extensions branch (~line 204–218):

FOUND_FILES=()
while IFS= read -r -d '' file; do
    FOUND_FILES+=("$file")
done < <(find "$DEFAULT_DOCS_DIR/" -maxdepth 10 -type f \( "${find_args[@]}" \) -print0 | sort -zV) || true

if [ ${#FOUND_FILES[@]} -eq 0 ]; then
     if [[ ${PIPESTATUS[0]} -ne 0 && ${PIPESTATUS[0]} -ne 1 ]]; then
         echo "Warning: Error running 'find' command in '$DEFAULT_DOCS_DIR' for tag '$TAG'."
     else
         echo "Warning: No files with extensions ... found ..."
     fi

Two independent reasons this can never fire:

1. find runs inside a process substitution < <( ... ). PIPESTATUS in the parent shell only ever reflects pipelines executed directly by the parent — it can never report the exit status of a command inside <( ).
2. By the time line 212 executes, the [ ${#FOUND_FILES[@]} -eq 0 ] test itself is the most recent pipeline, so PIPESTATUS[0] is ['s own status (0 when the count check passes... and 1 exactly when it enters this branch), never find's.

Repro (stock repo)

# point DEFAULT_DOCS_DIR at a missing directory and run the branch logic:
# find prints "find: /nonexistent-dir/: No such file or directory" to stderr,
# but the script reports:
#   Warning: No files with extensions (...) found in '...' for tag '<TAG>'.
# instead of the intended error message.

Practical impact during a real build: if docs/ is renamed or a checkout is broken for some tag, the operator sees "no docs found" (looks like an old tag that legitimately had no docs dir) instead of "find errored", which points at a different root cause.

Minimal fix

Route the pipeline through a temp file so its status is directly observable by the parent:

-        FOUND_FILES=()
-        while IFS= read -r -d '' file; do
-            FOUND_FILES+=("$file")
-        done < <(find "$DEFAULT_DOCS_DIR/" -maxdepth 10 -type f \( "${find_args[@]}" \) -print0 | sort -zV) || true
+        FOUND_FILES=()
+        FIND_TMP=$(mktemp)
+        FIND_STATUS=0
+        find "$DEFAULT_DOCS_DIR/" -maxdepth 10 -type f \( "${find_args[@]}" \) -print0 \
+            | sort -zV > "$FIND_TMP" || FIND_STATUS=$?
+        while IFS= read -r -d '' file; do
+            FOUND_FILES+=("$file")
+        done < "$FIND_TMP"
+        rm -f "$FIND_TMP"

and change the guard from ${PIPESTATUS[0]} to $FIND_STATUS.

Verified post-fix behavior (with set -eEo pipefail, matching the script):

Happy to send this as a PR if useful.

I run FreshContext ($5, version-anchored context packs for AI coding agents — current-doc links, deprecated-pattern traps, verification commands). This repo is basically the gold standard of that problem space, so no pitch needed here — just flagging the bug.

Start in build-docs.sh at the default-extensions branch around lines 204–218, where find runs inside process substitution and PIPESTATUS is checked. Reproduce the missing-directory case, then verify the reported find status, valid directories with matching files, and directories with no matching extensions. Done means these three cases produce the expected warnings or file count without relying on PIPESTATUS from process substitution.