docs: add TinyGo sync strategy documentation

CLAUDE.md

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+# Claude Code Guidelines
+
+## Documentation
+
+- [TinyGo Sync Strategy](docs/tinygo-sync-strategy.md) - Branch structure and workflow for syncing with TinyGo upstream

docs/tinygo-sync-strategy.md

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+# TinyGo Sync Strategy
+
+## Goals
+
+Establish a clear branch structure to enable us to:
+- Track TinyGo official updates
+- Clearly demonstrate our customizations on top of TinyGo
+- Facilitate code review and maintenance
+
+## Branch Structure
+
+### `machine` Branch
+- **Responsibility**: Pure mirror of TinyGo's official `src/machine` module
+- **Update Source**: https://github.com/tinygo-org/tinygo (src/machine/)
+- **Rules**: Sync only, no custom modifications
+- **Commit Tag**: `[SYNC] Update machine to TinyGo <version>`
+
+### `device` Branch
+- **Responsibility**: Pure mirror of TinyGo's official `src/device` module
+- **Update Source**: https://github.com/tinygo-org/tinygo (src/device/)
+- **Rules**: Sync only, no custom modifications
+- **Commit Tag**: `[SYNC] Update device to TinyGo <version>`
+
+### `main` Branch
+- **Responsibility**: Production code version (protected)
+- **Composition**: Merged from `machine` and `device` branches + our custom modifications
+- **Rules**: ⛔ No direct push, all changes must go through PR
+
+## Workflow
+
+### 1. Daily Development
+- Create development branch from main
+- Develop and commit
+- Create PR to main
+- Code review and merge
+- Clean up development branch
+
+### 2. Sync Upstream Updates
+- Update machine/device branches (commit with `[SYNC]`)
+- Create sync branch or directly create PR
+- Resolve conflicts (if any)
+- Code review and merge
+
+## Practical Use Cases
+
+### Case 1: Daily Feature Development
+
+**Scenario**: Add new features or modifications
+
+**Process**:
+1. Create development branch
+2. Develop and commit
+3. Create PR to main
+4. Review and merge
+
+---
+
+### Case 2: Merge Upstream Updates
+
+**Scenario**: TinyGo releases new version, sync to our repository
+
+**Notes**:
+- Do not directly track upstream dev branch
+- Track upstream minor version updates
+
+**Process**:
+1. Sync to machine branch (commit with `[SYNC]`)
+2. Sync to device branch (commit with `[SYNC]`)
+3. On main branch, sync files from machine and device branches
+4. Apply our custom modifications on the updated base (if needed)
+5. Create PR to main