compound-loop v0.7.0

Added

• Settled the plan status enum at draft | approved | done | superseded with terminal-state evidence fields (completed_by: for done, superseded_by: for superseded), rejection records for in-progress and abandoned, a mutable-slot boundary, and an applicability boundary for grandfathering.
• Shipped skills/planning/scripts/validate-plan-frontmatter.py — a pure-stdlib plan/v1 frontmatter validator with 27-case fixture harness, CWD-independent root derivation, and CPython 3.9–3.14 compilation.
• Gated the plan corpus in scripts/validate.sh (15 plans validated) and registered the validator in the Python compatibility harness.
• Added a carry-forward trigger audit step to skills/planning/SKILL.md with edit/drift/event-based classification and a reviewer re-derive mandate.
• Added carry-forward trigger audit and plan-schema hard-floor sections to schemas/plan-schema.md.
• skills/planning/SKILL.md now gates plan commits on the frontmatter validator and writes superseded status on predecessor plans.
• skills/retrospective/SKILL.md Phase 8 now flips covered plans to done atomically with the retro commit, with flip-all for multi-plan retros.
• skills/implementing/SKILL.md Pre-flight now refuses terminal-status plans naming the evidence field.
• Documented PEP 585 annotations crash and mandated-field-absent-from-schema as reusable solutions.

Fixed

• Compound frontmatter validator now runs cleanly on CPython 3.8 — replaced list[str] annotation with from __future__ import annotations placement.
• Plan frontmatter validator guards against list-valued scalar fields (TypeError crash) and validates completed_by through the scalar helper.