docs(post-mortem): Apply session start checklists and edit tool warnings

From gui_decoupling_controller track post-mortem:

workflow.md:
- Add mandatory session start checklist (6 items)
- Add code style section with 1-space indentation enforcement
- Add native edit tool warning with MCP alternatives

AGENTS.md:
- Add critical native edit tool warning
- Document MCP tool alternatives for file editing

tier1-orchestrator.md:
- Add session start checklist

tier2-tech-lead.md:
- Add session start checklist
- Add tool restrictions section (allowed vs forbidden)
- Add explicit delegation pattern

tier3-worker.md:
- Add task start checklist

tier4-qa.md:
- Add analysis start checklist

.opencode/agents/tier3-worker.md

@@ -46,6 +46,14 @@ You MUST use Manual Slop's MCP tools. Native OpenCode tools are unreliable.
 You operate statelessly. Each task starts fresh with only the context provided.
 Do not assume knowledge from previous tasks or sessions.
 
+## Task Start Checklist (MANDATORY)
+
+Before implementing:
+1. [ ] Read task prompt - identify WHERE/WHAT/HOW/SAFETY
+2. [ ] Use skeleton tools for files >50 lines (`manual-slop_py_get_skeleton`, `manual-slop_get_file_summary`)
+3. [ ] Verify target file and line range exists
+4. [ ] Announce: "Implementing: [task description]"
+
 ## Task Execution Protocol
 
 ### 1. Understand the Task