feat: add product capability planning lane

docs/examples/product-capability-template.md

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+# Product Capability Template
+
+Use this when product intent exists but the implementation constraints are still implicit.
+
+The purpose is to create a durable capability contract, not another vague planning doc.
+
+## Capability
+
+- **Capability name:**
+- **Source:** PRD / issue / discussion / roadmap / founder note
+- **Primary actor:**
+- **Outcome after ship:**
+- **Success signal:**
+
+## Product Intent
+
+Describe the user-visible promise in one short paragraph.
+
+## Constraints
+
+List the rules that must be true before implementation starts:
+
+- business rules
+- scope boundaries
+- invariants
+- rollout constraints
+- migration constraints
+- backwards compatibility constraints
+- billing / auth / compliance constraints
+
+## Actors and Surfaces
+
+- actor(s)
+- UI surfaces
+- API surfaces
+- automation / operator surfaces
+- reporting / dashboard surfaces
+
+## States and Transitions
+
+Describe the lifecycle in terms of explicit states and allowed transitions.
+
+Example:
+
+- `draft -> active -> paused -> completed`
+- `pending -> approved -> provisioned -> revoked`
+
+## Interface Contract
+
+- inputs
+- outputs
+- required side effects
+- failure states
+- retries / recovery
+- idempotency expectations
+
+## Data Implications
+
+- source of truth
+- new entities or fields
+- ownership boundaries
+- retention / deletion expectations
+
+## Security and Policy
+
+- trust boundaries
+- permission requirements
+- abuse paths
+- policy / governance requirements
+
+## Non-Goals
+
+List what this capability explicitly does not own.
+
+## Open Questions
+
+Capture the unresolved decisions blocking implementation.
+
+## Handoff
+
+- **Ready for implementation?**
+- **Needs architecture review?**
+- **Needs product clarification?**
+- **Next ECC lane:** `project-flow-ops` / `tdd-workflow` / `verification-loop` / other