feat(skills): add self-healing and verify-gate skills from pskoett-skills fork

Self-healing: heal loop with verify-before-persist discipline, Pattern-Key
dedup, HEAL entry format, 3 scripts, examples reference, eval.yaml.
Verify-gate: 4-step process (Discover -> Run -> Fix Loop -> Gate Signal)
with 3-attempt fix loop, scope-to-fix-only discipline, command discovery.
.learnings/HEALS.md with template entry.

.learnings/HEALS.md

@@ -0,0 +1,37 @@
+# Self-healing log
+
+Verified fixes for runtime failures. Each entry documents a failure, its root cause, the applied fix, and the verification proof.
+
+**Pattern-Key discipline:** before filing a new HEAL, search this file for an existing Pattern-Key. If found, increment `Recurrence-Count` and update `Last-Seen` — do not duplicate.
+
+**Lifecycle:** verified heals at Recurrence-Count ≥ 3 across distinct tasks get a `Handoff` block for promotion to project memory (`CLAUDE.md`, `AGENTS.md`, or a skill).
+
+---
+
+## [HEAL-YYYYMMDD-XXX] short_kebab_name
+
+**Logged**: ISO-8601 timestamp
+**Status**: pending-verify
+**Trigger**: tool-failure | missing-capability | env-issue | external-change | <free-form>
+**Area**: free-form tag (e.g. `build`, `tests`, `ci`, `auth`, `data-pipeline`)
+**Priority**: low | medium | high | critical
+
+### Failure
+Concrete error: command, error message, exit code, blocked action.
+
+### Diagnosis
+Root cause as understood after investigation. What was verified during diagnosis.
+
+### Fix
+Patch applied. Verbatim commands, code snippets, or pointers to `.learnings/heals/<HEAL-ID>/`.
+
+### Verification
+What was run after the fix and what it returned. Exit code, output snippet, test pass count. **Proof.**
+
+### Metadata
+- Related Files: path/to/file.ext
+- See Also: HEAL-... | LRN-... | ERR-...
+- Pattern-Key: lower.snake.case (e.g. `env.lockfile_mismatch`)
+- Recurrence-Count: 1
+- First-Seen: YYYY-MM-DD
+- Last-Seen: YYYY-MM-DD