docs: correct Agent Teams architecture + add session handoff template

## Agent Teams Architecture Corrections

Based on official sources (Addy Osmani blog, Feb 2026):

**Major changes**:
- Add mailbox system documentation (peer-to-peer messaging)
- Correct communication model: not only team lead synthesis
- Update diagrams to show peer-to-peer arrows
- Clarify context isolation vs message sharing
- Add 7 sections with source attribution
- Add documentation update note (2026-02-09)

**Key correction**: Agents communicate via mailbox system (direct
peer-to-peer + team lead synthesis), not only hierarchical reporting.

**Files modified**:
- guide/workflows/agent-teams.md (+72 -19): 7 major corrections
- CHANGELOG.md: Document session handoff template addition
- guide/architecture.md: Architecture clarifications
- guide/ultimate-guide.md: Cross-references updates

**Sources**:
- https://addyosmani.com/blog/claude-code-agent-teams/
- Perplexity research (sonar-reasoning-pro, Feb 2026)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

examples/templates/session-handoff-lorenz.md

@@ -0,0 +1,162 @@
+# Session Handoff Template
+
+**Inspired by**: [Robin Lorenz's Context Engineering approach](https://www.linkedin.com/posts/robin-lorenz-54055412a_claudecode-contextengineering-aiengineering-activity-7425136701515251713) (Feb 2026)
+
+**Purpose**: Structured handoff to preserve intent when approaching context limits. Triggers at **85% context usage** to prevent auto-compact quality degradation.
+
+---
+
+## Session Metadata
+
+**Date**: YYYY-MM-DD
+**Project**: [Project Name]
+**Context Trigger**: X% (recommended: 85%)
+**Session ID**: [Optional - for reference]
+
+---
+
+## ✅ Completed Work
+
+List all work finished in this session with commit references:
+
+- **[Task 1]**: Description of what was accomplished
+  - Commit: `abc123`
+  - Files: `src/feature.ts`, `tests/feature.test.ts`
+
+- **[Task 2]**: Another completed item
+  - Commit: `def456`
+  - Files: `config/settings.json`
+
+**Git status check**:
+```bash
+# Run before handoff to capture state
+git status
+git log -5 --oneline
+```
+
+---
+
+## 🔄 Pending Tasks
+
+Tasks started but not completed, with percentage and blockers:
+
+- **[Task 3]**: Brief description
+  - **Progress**: 80% complete
+  - **Blocker**: Waiting for API key / Need to clarify requirements
+  - **Next action**: [Specific next step]
+  - **Files touched**: `src/pending-feature.ts`
+
+- **[Task 4]**: Another pending item
+  - **Progress**: Research phase (20%)
+  - **Blocker**: Need architectural decision on X
+  - **Next action**: Review options A vs B
+
+---
+
+## 🚧 Blockers & Issues
+
+Critical blockers that need resolution before proceeding:
+
+1. **[Blocker 1]**: Detailed description of what's blocking progress
+   - **Impact**: What this blocks
+   - **Workaround**: Temporary solution if any
+   - **Resolution path**: How to unblock
+
+2. **[Issue 1]**: Technical debt or bug discovered
+   - **Severity**: High/Medium/Low
+   - **Workaround**: Current mitigation
+
+---
+
+## ➡️ Next Steps
+
+Prioritized action items for the next session:
+
+1. **[High Priority]**: First action to take when resuming
+2. **[High Priority]**: Second critical action
+3. **[Medium]**: Follow-up task after priorities
+4. **[Low]**: Nice-to-have or exploratory task
+
+**Immediate start**: When resuming, begin with [specific file/task].
+
+---
+
+## 📌 Essential Context
+
+Critical information that MUST be preserved (decisions, patterns, constraints):
+
+### Architectural Decisions
+- **Decision 1**: We chose approach X over Y because [rationale]
+- **Pattern established**: All new features must follow [pattern]
+
+### Technical Constraints
+- **Constraint 1**: Can't use library X due to [reason]
+- **Constraint 2**: Must maintain compatibility with [system]
+
+### Domain Knowledge
+- **Business rule**: Important rule discovered during implementation
+- **Edge case**: [Unusual scenario] requires [special handling]
+
+### Dependencies
+- **External**: Waiting on [team/service] for [dependency]
+- **Internal**: Feature X depends on completion of Y
+
+---
+
+## 🔄 Resume Instructions
+
+**For next session**:
+
+```bash
+# Load this handoff into new session
+cat claudedocs/handoffs/handoff-YYYY-MM-DD.md | claude -p
+
+# Or reference manually
+claude
+# Then: "Continue from handoff document in claudedocs/handoffs/handoff-YYYY-MM-DD.md"
+```
+
+**Context check**:
+```bash
+# After resuming, verify context state
+/status
+```
+
+**If context still high (>70%)**: Consider breaking into smaller focused sessions.
+
+---
+
+## 📊 Session Stats (Optional)
+
+- **Turns**: ~X (approaching degradation threshold at 15-25 turns)
+- **Context usage**: X% (triggered handoff at 85%)
+- **Duration**: X hours
+- **Commits**: X commits pushed
+
+---
+
+## 💡 Why This Template?
+
+**Research-backed rationale**:
+
+- **Auto-compact degrades quality**: LLM performance drops 50-70% on complex tasks at high context ([Context Rot Research](https://research.trychroma.com/context-rot))
+- **Manual handoff preserves intent**: Structured documentation captures "what matters" vs "degraded version of everything"
+- **85% threshold prevents auto-compact**: Auto-compact triggers at ~75% (VS Code) or ~95% (CLI), so 85% provides safety margin
+- **Logical breakpoint > automatic compression**: Community consensus favors manual `/compact` at breakpoints
+
+**Key principle**: "A handoff gives you a clean version of what matters" — Robin Lorenz
+
+---
+
+## 📚 Related Resources
+
+- [Session Handoffs (Ultimate Guide)](../../guide/ultimate-guide.md#session-handoffs)
+- [Auto-Compaction Research (Architecture)](../../guide/architecture.md#auto-compaction)
+- [Fresh Context Pattern (Ultimate Guide)](../../guide/ultimate-guide.md#fresh-context-pattern)
+- [Lorenz's Original Post](https://www.linkedin.com/posts/robin-lorenz-54055412a_claudecode-contextengineering-aiengineering-activity-7425136701515251713)
+
+---
+
+**Template Version**: 1.0
+**Last Updated**: 2026-02-08
+**Maintenance**: Update as research evolves