fix(lint): make the Unicode-space regex actually match Unicode spaces (#3027)

The `Lint workflows` autofix job has failed on every scheduled run since at
least 2026-08-16, with `shfmt` reporting parse errors ("LitWord cannot be
followed by a word", "${ stmts;} is a mksh feature", ...) in ~70 shell scripts
that parse cleanly on a pristine checkout.

Root cause is the preceding "Fix non-printable Unicode spaces" step. Its regex
was written as `$'[\\u00A0\\u2002...]'`: the doubled backslash makes bash's
ANSI-C quoting emit the literal text ` `, and Perl has no `\u` codepoint
escape — `\u` is the titlecase-next-character operator, so the character class
degrades to the plain characters `0 2 3 5 7 8 9 A B F`. The step therefore
replaced those digits and letters with spaces in every text file in the repo,
which is what left the shell scripts unparseable. `shfmt` then exited 1 and the
job stopped before opening its autofix PR — the only reason the corruption was
never committed.

Switch to Perl's own `\x{...}` escape in a plain single-quoted string, so the
class holds the ten intended code points and nothing else.

Verified locally against the exact step body extracted from the workflow: on a
sample of the repo it now rewrites only the real U+202F occurrences (e.g.
`postgres_15/.../99-run.sh`, `birdnet-pi/DOCS.md`) and leaves all other text
untouched, and `shfmt v3.12.0 -w -i 4 -ci -bn -sr` over the whole repo exits 0
with no parse errors.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

.github/workflows/lint.yml

@@ -38,7 +38,7 @@ jobs:
         run: |
           set -euo pipefail
           CHANGED_FILES=$(git diff --name-only "$DIFF_RANGE")
-          UNICODE_SPACES_REGEX=$'[\\u00A0\\u2002\\u2003\\u2007\\u2008\\u2009\\u202F\\u205F\\u3000\\u200B]'
+          UNICODE_SPACES_REGEX='[\x{00A0}\x{2002}\x{2003}\x{2007}\x{2008}\x{2009}\x{202F}\x{205F}\x{3000}\x{200B}]'
           for file in $CHANGED_FILES; do
             if [ -f "$file" ]; then
               MIME_TYPE=$(file --mime-type -b "$file")
@@ -89,7 +89,7 @@ jobs:
       - name: Fix non-printable Unicode spaces in all text files
         run: |
           set -euo pipefail
-          UNICODE_SPACES_REGEX=$'[\\u00A0\\u2002\\u2003\\u2007\\u2008\\u2009\\u202F\\u205F\\u3000\\u200B]'
+          UNICODE_SPACES_REGEX='[\x{00A0}\x{2002}\x{2003}\x{2007}\x{2008}\x{2009}\x{202F}\x{205F}\x{3000}\x{200B}]'
           find . -type f ! -path "./.git/*" | while read -r file; do
             MIME_TYPE=$(file --mime-type -b "$file")
             if [[ "$MIME_TYPE" == text/* ]]; then