✨ feat(workflow): adopt Matt Pocock ticket workflow

Replace the Superpowers plan pipeline with grill-with-docs, specs, local tickets, and ticket-native execution.

BREAKING CHANGE: Remove the legacy Plan CLI, prompt templates, and Superpowers skills.

skills/thirdparty/grill-with-docs/SKILL.md

@@ -0,0 +1,7 @@
+---
+name: grill-with-docs
+description: A relentless interview to sharpen a plan or design, which also creates docs (ADR's and glossary) as we go.
+disable-model-invocation: true
+---
+
+Run a `/grilling` session, using the `/domain-modeling` skill.

skills/thirdparty/grill-with-docs/agents/openai.yaml

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+interface:
+  display_name: "Grill with Docs"
+  short_description: "Grill a design and write its docs"
+policy:
+  allow_implicit_invocation: false