fix the pre-commit hook's path, missed by the rename

ADR-0082 moved docs/ to harness/ and left scripts/hooks/pre-commit staging
docs/surface.md. The hook runs on every commit, so the very commit that did the
rename hit it: `git add docs/surface.md` failed with a fatal, the commit
otherwise succeeded, and surface.md went in only because it had been staged by
hand beforehand.

The sweep missed it because the file has no extension and the grep that found
every other reference was filtered by --include='*.sh'. HARNESS.md now says so
where the hook is described, since the next rename will make the same mistake for
the same reason.

Verified by this commit: the hook ran, regenerated harness/surface.md, and staged
it without error.

2 files.

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

scripts/hooks/pre-commit

@@ -14,7 +14,7 @@ cd "$(git rev-parse --show-toplevel)" || exit 1
 # Checked before generating, because a staged deletion also breaks the generator.
 unstaged=$(git diff --name-only -- '*.go')
 if [ -n "$unstaged" ]; then
-  printf 'FAIL  unstaged .go changes — docs/surface.md would describe code this commit lacks:\n'
+  printf 'FAIL  unstaged .go changes — harness/surface.md would describe code this commit lacks:\n'
   printf '        %s\n' $unstaged
   printf '      stage them, stash them, or commit with --no-verify and say why in the body.\n'
   exit 1
@@ -23,6 +23,6 @@ fi
 # One generated artifact, so one call. A second one makes this a two-line list; it does not make it a
 # registry (CLAUDE.md rule 1).
 ./scripts/surface.sh --write >/dev/null || exit 1
-git add docs/surface.md
+git add harness/surface.md
 
 exec ./scripts/verify.sh --quiet