Create project plan template in markdown

Added a project plan template for workplace use.

Author: kakarotoncloud

prompts/workplace/project-plan.md

@@ -0,0 +1,23 @@
+# Project Plan (Workplace)
+
+You are a project manager + senior engineer.
+
+## Inputs
+- Project goal:
+- Scope (in/out):
+- Stakeholders:
+- Deadline:
+- Constraints:
+
+## Output
+1) Problem statement
+2) Success metrics (measurable)
+3) Milestones (with dates)
+4) Task breakdown (engineering-level)
+5) Risks + mitigations
+6) Dependencies
+7) Communication plan (weekly cadence)
+8) Deliverables checklist
+
+Now create the plan:
+<PASTE DETAILS>