v3.16.0 — self-amending loop, /interview-me + /spec, anti-rationalization tables, duplicate guard

MINOR — developer-workflows 0.19.0 → 0.21.1: three feature clusters + one direct fix. No breaking changes; every existing workflow is byte-identical unless the new commands are explicitly invoked.

Added

• /interview-me — hypothesis-driven one-question-at-a-time brief extraction; stops at ≥ 95% confidence; feeds into /spec or /plan.
• /spec — writes a 6-section PRD to .harness/SPEC.md before planning; /plan reads it as structured input when present.
• Self-amending loop — autonomous correction cycle: disposition classifier (kernel-defect vs operator-tuning), amend-and-ship with CI-before-tag wiring, correction quality gate, end-to-end dogfood seed validation. See ADR 0030.
• Single-writer artifact integration — integrate_worker.py serializes merges; concurrent-release coordination; pre-flight reconcile against already-shipped lanes; no-bypass conformance guard.
• capabilities.json sidecar (emit-antigravity) — each plugin emits a capabilities.json for host-side capability discovery.
• Anti-rationalization tables — ## Common Rationalizations two-column tables in /work (3 rows), /bugfix (3 rows), /review (2 rows); fire at invocation time to make step-skipping excuses immediately visible and refuted.
• Anatomy Patterns section in wiki/reference/Add-A-Skill.md — documents Rationalizations table + Red Flags list formats with /work examples.

Fixed

• Duplicate guard in /work step 1 — Status: done or live worker/<slug> branch on origin → immediate DUPLICATE GUARD stop instead of silently re-doing the work.
• _posix_bash resolver — skips WSL bash stub on Windows (returned exit 0 but wasn't real bash).
• capabilities.json sidecars left untracked by emit-antigravity generator.

Internal

• developer-workflows 0.19.0 → 0.21.1 across two integrated worker plans + one direct fix.
• ADR 0030 authored and finalized — generated-artifact single-writer contract.
• 19 commits, check-all 10/10 PASS.