Remove auto-chain handoffs from all pipeline phases

Each speckit phase (specify, plan, tasks, implement) previously had
`handoffs` with `send: true`, causing the entire pipeline to fire as
one unstoppable chain. This creates critical issues in automated/headless
environments:

- Session contamination when phases inherit stale context from prior runs
- Zombie processes from auto-chained phases that survive process kills
- Wrong-issue execution when environment is reused across issues
- Loss of orchestrator control between phases (no verify step possible)

Fix: remove all handoff frontmatter so each phase completes its work,
reports what it did, and stops. The caller decides when to advance.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Max

templates/commands/implement.md

@@ -1,10 +1,5 @@
 ---
 description: Execute tasks from tasks.md
-handoffs:
-  - label: Analyze
-    agent: speckit.analyze
-    prompt: Check implementation consistency
-    send: true
 ---
 
 **INPUT**: `$ARGUMENTS`

templates/commands/plan.md

@@ -1,13 +1,5 @@
 ---
 description: Create technical implementation plan from specification
-handoffs:
-  - label: Tasks
-    agent: speckit.tasks
-    prompt: Generate task list
-    send: true
-  - label: Checklist
-    agent: speckit.checklist
-    prompt: Validate plan quality
 ---
 
 **INPUT**: `$ARGUMENTS`

templates/commands/specify.md

@@ -1,14 +1,5 @@
 ---
 description: Create feature specification from GitHub issue
-handoffs:
-  - label: Plan
-    agent: speckit.plan
-    prompt: Create technical plan
-    send: true
-  - label: Clarify
-    agent: speckit.clarify
-    prompt: Resolve open questions
-    send: true
 ---
 
 **INPUT**: `$ARGUMENTS`

templates/commands/tasks.md

@@ -1,14 +1,5 @@
 ---
 description: Generate actionable task list from plan
-handoffs:
-  - label: Implement
-    agent: speckit.implement
-    prompt: Execute tasks
-    send: true
-  - label: Analyze
-    agent: speckit.analyze
-    prompt: Check consistency
-    send: true
 ---
 
 **INPUT**: `$ARGUMENTS`