fix(hooks): pre-commit fails in any worktree without a Makefile, so a non-code worktree cannot commit #678

Area: infra / hooks · bug · found by the pm-triage daily routine, which it blocks outright

Expected: .githooks/pre-commit gates commits that contain code. A worktree that holds no code has nothing to verify and should commit.

Actual: core.hooksPath is set in .git/config to an absolute path (<checkout>/.githooks), so the hook runs in every linked worktree, including ones that do not contain the repo's tree. The hook does cd "$(git rev-parse --show-toplevel)", which in a linked worktree is that worktree's own root, and then:

• scripts/ci-marker.sh has-verify-marker is not found there, and its error is swallowed by 2>/dev/null, so the marker shortcut cannot be taken;
• make verify finds no Makefile and fails with make: *** No rule to make target 'verify'. Stop. (GNU make's wording when a target is named and no makefile exists);
• the hook prints 🛑 pre-commit: 'make verify' failed. and exits 1.

Reproduced at 4ff50745 by running the hook's own body from the pm-triage-state worktree.

Impact: no commit can be made in such a worktree, and --no-verify is not available to an agent session. The pm-triage routine keeps its state on the orphan branch pm-triage-state (three text files, no code, never pushed) and calls state.sh commit at the end of every run; that call now fails, so the routine loses its versioned audit trail. It still functions — state.sh read reads the file, not git — but each run's record goes uncommitted. Any future non-code worktree hits the same wall.

Scope: the hook has no business running where there is no tree to verify — an early [ -f Makefile ] || exit 0 is the whole fix. Leaving scripts/ci-marker.sh's failure silent under 2>/dev/null is what turned a missing file into a confusing make error; a missing-script case worth distinguishing from a missing marker.

Related: #170 (which added the tree-keyed marker), #454, #565

From the pm-triage daily routine (2026-09-28), which this blocked; reproduced against 4ff50745.