✨ 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/handoff/SKILL.md

@@ -0,0 +1,16 @@
+---
+name: handoff
+description: Compact the current conversation into a handoff document for another agent to pick up.
+argument-hint: "What will the next session be used for?"
+disable-model-invocation: true
+---
+
+Write a handoff document summarising the current conversation so a fresh agent can continue the work. Save to the temporary directory of the user's OS - not the current workspace.
+
+Include a "suggested skills" section in the document, which suggests skills that the agent should invoke.
+
+Do not duplicate content already captured in other artifacts (specs, plans, ADRs, issues, commits, diffs). Reference them by path or URL instead.
+
+Redact any sensitive information, such as API keys, passwords, or personally identifiable information.
+
+If the user passed arguments, treat them as a description of what the next session will focus on and tailor the doc accordingly.

skills/thirdparty/handoff/agents/openai.yaml

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+interface:
+  display_name: "Handoff"
+  short_description: "Compact a conversation into a handoff"
+policy:
+  allow_implicit_invocation: false