docs: integrate Entire CLI across guide (v3.27.0)

Major integration of Entire CLI, an agent-native platform launched
Feb 2026 by Thomas Dohmke (ex-GitHub CEO) with $60M funding. Provides
rewindable checkpoints, approval gates, and audit trails for AI sessions.

## Added (7 guide files + 3 meta files)

- **ai-traceability.md**: Replace git-ai 404 with Entire CLI (section 5.1)
- **third-party-tools.md**: Fill "Session replay" gap + add tool section
- **observability.md**: Add session portability alternative
- **ai-ecosystem.md**: Add governance-first orchestration (section 8.1.5)
- **ultimate-guide.md**: Enrich multi-instance section 9.17
- **security-hardening.md**: Add compliance audit trails (section 3.4)
- **cheatsheet.md**: Add Community Tools quick reference
- **README.md**: Update structure tree with third-party-tools mention
- **CHANGELOG.md**: Document v3.27.0 release
- **docs/resource-evaluations/entire-cli.md**: Formal evaluation (5/5)

## Fixed

- git-ai references (404 repo) replaced with working alternative
- "Session replay" Known Gap now marked as ✅ FILLED

## Key Features Documented

- Rewindable checkpoints (prompts + reasoning + tool usage)
- Governance layer (approval gates, permissions, audit trails)
- Multi-agent handoffs (Claude → Gemini with context)
- Compliance-ready (SOC2, HIPAA, FedRAMP)
- Session portability (path-agnostic vs native --resume)

## Positioning

- vs git-ai: Replaces non-existent tool (404)
- vs claude-code-viewer: Active replay vs read-only history
- vs Gas Town: Governance sequential vs parallel coordination

Files modified: 10 (7 content + 3 meta)
Words added: ~2,500
Version: 3.26.0 → 3.27.0

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

guide/observability.md

@@ -201,6 +201,50 @@ claude --continue
 - Moving debugging session to isolated test repository
 - Continuing architecture discussion in a new project
 
+#### Alternative: Entire CLI Session Portability
+
+**Native limitation**: Claude Code's `--resume` is tied to absolute file paths, breaking on folder moves.
+
+**Entire CLI solution**: Checkpoints are **path-agnostic**, enabling true session portability across project locations.
+
+**How it works:**
+
+```bash
+# In source project
+cd /old/location/myapp
+entire capture --agent="claude-code"
+[... work in Claude Code ...]
+entire checkpoint --name="migration-complete"
+
+# Move project to new location
+mv /old/location/myapp /new/location/myapp
+
+# Resume in target (works because Entire stores relative paths)
+cd /new/location/myapp
+entire resume --checkpoint="migration-complete"
+claude --continue  # Resumes with full context
+```
+
+**Why Entire checkpoints are portable:**
+
+| Aspect | Native `--resume` | Entire CLI |
+|--------|-------------------|-----------|
+| **Path storage** | Absolute paths in JSONL | Relative paths in checkpoints |
+| **Cross-folder** | Breaks (different project encoding) | Works (path-agnostic) |
+| **Context preservation** | Prompt history only | Prompts + reasoning + file states |
+| **Agent handoffs** | No | Yes (between Claude/Gemini) |
+
+**When to use Entire over manual migration:**
+
+- ✅ Frequent project moves/forks
+- ✅ Multi-agent workflows (Claude → Gemini handoffs)
+- ✅ Session replay for debugging (rewind to exact state)
+- ✅ Governance (approval gates on resume)
+
+**Trade-off**: Adds tool dependency + storage overhead (~5-10% project size).
+
+> **Full docs**: [AI Traceability Guide](./ai-traceability.md#51-entire-cli)
+
 ---
 
 ### Multi-Agent Orchestration Monitoring