test: add skill validation tests; fix stale make-target refs in skills

- New tests/unit/test_skills_validation.py: structure, make-target,
  file-ref checks + existence tests for all 10 skills
- testing-and-debugging: fix molecule count (6->7), drop
  molecule-all-parallel/pre-push/lint-ci refs (not grm targets),
  add When to Invoke + Prerequisites
- devx-workflow: fix rebase targets (devx-rebase/devx-pr-rebase),
  add When to Invoke + Prerequisites
- spec-driven-development: add When to Invoke + Prerequisites

.devin/skills/devx-workflow/SKILL.md

@@ -2,6 +2,16 @@
 
 Quick reference for devx tools when working on this repo.
 
+## When to Invoke
+
+Invoke this skill when creating PRs, checking CI status, adding
+labels, rebasing branches, or performing any PR lifecycle operation.
+
+## Prerequisites
+
+- `.venv` exists (run `make setup` if not)
+- `.env` with `DEVELOPER_GITEA_API_TOKEN`, `VIKUNJA_TOKEN`
+
 ## PR Workflow (use these, not raw git/tea/MCP)
 
 | Task | Command |
@@ -12,8 +22,8 @@ Quick reference for devx tools when working on this repo.
 | Check CI status | `make devx-pr-status` or `make devx-pr-status PR=42 WAIT=1` |
 | Fetch CI failure logs | `make devx-pr-logs` or `make devx-pr-logs PR=42 JOB=quality TAIL=50` |
 | Add ready-to-merge label | `make devx-pr-label` or `make devx-pr-label PR=42` |
-| Rebase current branch | `make rebase` |
+| Rebase current branch | `make devx-rebase` |
-| Rebase PR via API | `make pr-rebase` or `make pr-rebase PR=42` |
+| Rebase PR via API | `make devx-pr-rebase` or `make pr-rebase PR=42` |
 
 ## Auto-merge Behavior
 

.devin/skills/spec-driven-development/SKILL.md

@@ -1,5 +1,14 @@
 # Spec-Driven Development
 
+## When to Invoke
+
+Invoke this skill when starting any change — every PR requires a spec
+at `docs/specs/<TASK-ID>.md` that CI validates before merge.
+
+## Prerequisites
+
+- A Vikunja task ID (`GRM-N`) — see `vikunja-tasks` skill
+
 ## Overview
 
 Every change starts with a spec. No spec, no code. No code, no PR.

.devin/skills/testing-and-debugging/SKILL.md

@@ -3,6 +3,17 @@
 Make targets for testing, debugging, and CI investigation. **Use these
 instead of raw `pytest`, `ruff`, or `molecule` commands.**
 
+## When to Invoke
+
+Invoke this skill when running tests, investigating CI failures, or
+debugging molecule scenarios. Also invoke when asked to "run tests",
+"check coverage", or "debug a failure".
+
+## Prerequisites
+
+- `.venv` exists (run `make setup` if not)
+- For molecule tests: Docker is running
+
 ## Why Make Targets
 
 Make targets encapsulate the correct venv activation, PYTHONPATH, env
@@ -31,9 +42,8 @@ produces false failures (missing dependencies, wrong Python version).
 
 | Task | Command | Notes |
 |------|---------|-------|
-| All scenarios | `make molecule` | All 6 scenarios on Ubuntu 22.04 |
+| All scenarios | `make molecule` | All 7 scenarios on Ubuntu 22.04 |
-| All platforms | `make molecule-all` | All 6 scenarios on all 4 OSes |
+| All platforms | `make molecule-all` | All 7 scenarios on all 4 OSes |
-| Parallel | `make molecule-all-parallel` | MOLECULE_JOBS=4 |
 
 ### Spec-Driven Workflow
 
@@ -46,12 +56,12 @@ CI validates the spec before running expensive jobs.
 **Before pushing any branch:**
 
 ```bash
-make pre-push
+make lint-all && make pytest-cov
 ```
 
-This runs `lint-all` + `pytest-cov`. The pre-push git hook only
+This runs all linters + unit tests with coverage. The pre-push git
-validates the Vikunja task exists — it does NOT run tests. You must
+hook only validates the Vikunja task exists — it does NOT run tests.
-run `make pre-push` manually.
+Run the checks manually (there is no `pre-push` target here).
 
 ## CI Failure Investigation
 
@@ -59,7 +69,7 @@ When investigating a CI failure:
 
 1. **Fetch logs via MCP** — use `mcp_call_tool` with gitea server,
    `actions_run_read` method, `download_job_log` tool
-2. **Reproduce locally** — use `make pytest-cov` or `make lint-ci`
+2. **Reproduce locally** — use `make pytest-cov` or `make lint-all`
    depending on which CI job failed
 3. **Never run raw pytest** — always use the make target
 

tests/unit/test_skills_validation.py

@@ -0,0 +1,120 @@
+"""Pytest tests for Devin skill validation.
+
+Validates that all skills in .devin/skills/ are well-formed: H1 title,
+"when to invoke" section, prerequisites when commands are referenced,
+make-target references that exist, and file references that exist.
+
+Run with: make pytest TEST=tests/test_skills_validation.py
+"""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+import pytest
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+
+# Sections required for every skill
+REQUIRED_SECTIONS = ["when to invoke"]
+
+# Sections required only for skills that reference commands/tools
+COMMAND_REQUIRED_SECTIONS = ["prerequisites"]
+
+# Markers indicating a skill references commands/tools
+COMMAND_MARKERS = ("`make ", "```bash", "```sh", "curl ", "python ", "python3 ", "ssh ")
+
+EXPECTED_SKILLS = [
+    "dependency-graph",
+    "deployment-coordination",
+    "devx-workflow",
+    "molecule-testing",
+    "pr-review",
+    "runner-ops",
+    "skill-creation",
+    "spec-driven-development",
+    "testing-and-debugging",
+    "vikunja-tasks",
+]
+
+
+def _find_skills() -> dict[str, Path]:
+    skills_dir = REPO_ROOT / ".devin" / "skills"
+    assert skills_dir.exists(), ".devin/skills/ directory not found"
+    return {d.name: d / "SKILL.md" for d in skills_dir.iterdir() if d.is_dir() and (d / "SKILL.md").exists()}
+
+
+# Skills shared with other repos — file-path references are only checked
+# in the owning repo (infra), where the referenced files live.
+SHARED_SKILLS = {"cross-repo-sync", "branch-hygiene", "dependency-graph", "skill-creation"}
+
+
+def _make_targets() -> set[str]:
+    """Collect make targets from Makefile plus included devx .mak files."""
+    targets: set[str] = set()
+    makefile = REPO_ROOT / "Makefile"
+    if makefile.exists():
+        targets.update(re.findall(r"^([a-zA-Z][a-zA-Z0-9_-]*):", makefile.read_text(), re.MULTILINE))
+    for mak in REPO_ROOT.glob(".venv/lib/python*/site-packages/devx/make/*.mak"):
+        targets.update(re.findall(r"^([a-zA-Z][a-zA-Z0-9_-]*):", mak.read_text(), re.MULTILINE))
+    return targets
+
+
+def _validate_skill(skill_name: str, skill_path: Path, make_targets: set[str]) -> list[str]:
+    """Validate a single skill file. Returns list of error messages."""
+    errors: list[str] = []
+    content = skill_path.read_text()
+
+    if not re.search(r"^# ", content, re.MULTILINE):
+        errors.append(f"{skill_name}: missing H1 title")
+
+    lower = content.lower()
+    for section in REQUIRED_SECTIONS:
+        if f"## {section}" not in lower:
+            errors.append(f"{skill_name}: missing '## {section.title()}' section")
+
+    references_commands = any(marker in content for marker in COMMAND_MARKERS)
+    if references_commands:
+        for section in COMMAND_REQUIRED_SECTIONS:
+            if f"## {section}" not in lower:
+                errors.append(
+                    f"{skill_name}: missing '## {section.title()}' section "
+                    "(required because skill references commands/tools)"
+                )
+
+    for target in re.findall(r"`make ([a-zA-Z][a-zA-Z0-9_-]*)`", content):
+        if target not in make_targets:
+            errors.append(f"{skill_name}: references `make {target}` but target does not exist")
+
+    # File-path checks: skip shared skills (checked in infra) and
+    # placeholder paths containing <...> templates.
+    if skill_name not in SHARED_SKILLS:
+        for match in re.findall(r"`((?:scripts|src|ansible|docs|tests|environments)/[^`\s]+)`", content):
+            if "<" in match:
+                continue
+            if not (REPO_ROOT / match).exists():
+                errors.append(f"{skill_name}: references `{match}` but file does not exist")
+
+    return errors
+
+
+@pytest.mark.parametrize("skill_name", EXPECTED_SKILLS)
+def test_skill_exists(skill_name: str) -> None:
+    """Each expected skill must have a SKILL.md."""
+    skill = REPO_ROOT / ".devin" / "skills" / skill_name / "SKILL.md"
+    assert skill.exists(), f"{skill_name}/SKILL.md not found"
+
+
+def test_minimum_skill_count() -> None:
+    """The repo should carry a working set of skills, not a stub."""
+    assert len(_find_skills()) >= 8, "expected >=10 skills"
+
+
+def test_all_skills_validate() -> None:
+    """All skills must pass structure/reference validation."""
+    make_targets = _make_targets()
+    errors: list[str] = []
+    for skill_name, skill_path in _find_skills().items():
+        errors.extend(_validate_skill(skill_name, skill_path, make_targets))
+    assert not errors, "Skill validation failed:\n" + "\n".join(f"  - {e}" for e in errors)