agent: repoint roles to frank-medium/dankclaw-3090; sync niri tweaks, memories, managed skills

- config.yml: default/commit -> frank-medium (dankserver); task/tiny/smol/vision -> frank-small (dankclaw-3090); vision xhigh
- models.yml: add llamacpp (dankclaw-3090) provider; frank-large preserve_thinking + context notes
- niri: focus-ring/border/shadow layout, hot-corners off, re-add noctalia.kdl include; blankpad eDP-1 scale 1.0
- memories: flush rollouts; retire frank_large + marreta_authentik skills; add auth-chain/kv-pool/quadlet-log skills
- managed-skills: 40+ new fleet runbook skills
- agent/skills: import built-in skill set

agent/skills/implement/SKILL.md

@@ -0,0 +1,15 @@
+---
+name: implement
+description: "Implement a piece of work based on a spec or set of tickets."
+disable-model-invocation: true
+---
+
+Implement the work described by the user in the spec or tickets.
+
+Use /tdd where possible, at pre-agreed seams.
+
+Run typechecking regularly, single test files regularly, and the full test suite once at the end.
+
+Once done, use /code-review to review the work.
+
+Commit your work to the current branch.