add marketplace plugin structure

plugins/pm-delivery/skills/retro-analysis/SKILL.md

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+---
+name: retro-analysis
+description: Analyse sprint delivery data and produce a structured retrospective brief
+tool_integration: Jira, Miro
+---
+# Retrospective Analysis Skill
+
+## Purpose
+Generate a data-grounded retrospective brief that separates facts from feelings, so the team spends retro time on solutions rather than debating what happened.
+
+## Required Inputs
+- Sprint tickets: planned vs. completed
+- Carry-over tickets and reasons
+- Tickets reopened after closing
+- Any incidents or unplanned work
+- Sprint velocity vs. historical average
+
+## Process
+1. Calculate: completion rate, carry-over rate, unplanned work percentage
+2. Identify patterns: which ticket types were most likely to carry over? Which caused blockers?
+3. Note any process or communication breakdowns visible in the data
+4. Prepare 3 "Start / Stop / Continue" prompts based on the data — not generic, specific to this sprint
+5. Suggest 1 concrete experiment for the next sprint based on the biggest friction point
+
+## Output Format
+
+### Sprint [Number] Retrospective Brief
+
+**By the Numbers:**
+- Planned: [n] tickets | Completed: [n] | Carry-over: [n] | Completion rate: [%]
+- Unplanned work: [n] tickets ([%] of capacity)
+- Velocity: [points] vs. [average] average
+
+**What the Data Suggests:**
+[2-3 observations grounded in the numbers above]
+
+**Discussion Prompts:**
+- Start: [specific prompt]
+- Stop: [specific prompt]
+- Continue: [specific prompt]
+
+**Suggested Experiment for Next Sprint:**
+[One concrete, testable process change]