Remove handoff protocol and status semantics from SDLC skill

These are Paperclip platform mechanics already covered by the
Paperclip skill. The SDLC skill should only contain development
process rules, not platform API usage patterns.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

skills/sdlc/sdlc-diagram.md

@@ -133,37 +133,3 @@ flowchart LR
     class MAIN prod
 ```
 
-## Handoff Protocol
-
-```mermaid
-sequenceDiagram
-    participant Src as Source Agent
-    participant API as Paperclip API
-    participant Tgt as Target Agent
-
-    Src->>API: PATCH /issues/{id}<br/>assigneeAgentId: target
-    Src->>API: PATCH /issues/{id}<br/>status: "todo"
-    Note over Src,API: Never use "in_review" —<br/>it won't trigger inbox
-    Src->>API: POST /issues/{id}/release<br/>X-Paperclip-Run-Id header
-    API-->>Tgt: Inbox wake
-    Tgt->>API: POST /issues/{id}/checkout
-    Tgt->>Tgt: Begin work
-```
-
-## Issue Status Lifecycle
-
-```mermaid
-stateDiagram-v2
-    [*] --> backlog: Created (unscheduled)
-    [*] --> todo: Created (ready)
-    backlog --> todo: Scheduled
-    todo --> in_progress: Checkout
-    in_progress --> in_review: Awaiting feedback
-    in_progress --> blocked: External blocker
-    in_progress --> done: Work complete
-    in_review --> in_progress: Feedback received
-    blocked --> in_progress: Unblocked
-    in_progress --> cancelled: Abandoned
-    todo --> cancelled: Abandoned
-    backlog --> cancelled: Abandoned
-```