Update docs, changelog, examples, and add ADRs for v1.2

- Add v1.1.0 and v1.2.0 changelog entries
- Add exclude field to config reference and example config
- Add ADRs documenting all major design decisions
- Fix step numbering in reverse_sync()
- Fix action.yml to copy VERSION file
- Add dist/ and .env to .gitignore
- Use refs/tags/ format for Nix flake tag refs

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

docs/adr/002-state-on-orphan-branch.md

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+# ADR-002: State Storage on Orphan Git Branch
+
+**Status:** Accepted
+**Date:** 2026-01
+
+## Context
+
+Josh-sync needs persistent state to track what has already been synced (last-synced commit SHAs, timestamps, status). This prevents re-syncing unchanged content and enables incremental operation. The state must survive CI runner teardown — runners are ephemeral containers.
+
+### Alternatives considered
+
+1. **File in the repo**: Commit a state JSON file to the monorepo. Every sync run creates a commit, polluting history. Race conditions when multiple sync jobs run concurrently.
+
+2. **External database/KV store**: Redis, SQLite, or a cloud KV service. Adds an infrastructure dependency. Credentials and connectivity to manage.
+
+3. **CI artifacts/cache**: Platform-specific (GitHub Actions cache, Gitea cache). Not portable across CI platforms. Expiry policies vary.
+
+4. **Orphan git branch**: A branch with no parent relationship to the main history. Stores JSON files in a simple `<target>/<branch>.json` layout. Pushed to origin, so it survives runner teardown. No external dependencies — uses git itself.
+
+## Decision
+
+Store sync state as JSON files on an orphan branch (`josh-sync-state`) in the monorepo.
+
+### Storage layout
+
+```
+origin/josh-sync-state/
+  <target>/<branch>.json       # sync state per target/branch
+  <target>/onboard.json        # onboard workflow state (v1.1+)
+```
+
+### Implementation
+
+- `read_state()`: `git fetch origin josh-sync-state && git show origin/josh-sync-state:<key>.json`
+- `write_state()`: Uses `git worktree` to check out the orphan branch in a temp directory, writes JSON, commits, and pushes. This avoids touching the main working tree.
+
+## Consequences
+
+**Positive:**
+- Zero external dependencies — only git
+- Portable across CI platforms (Gitea Actions, GitHub Actions, local)
+- Human-readable JSON files — easy to inspect and debug
+- Atomic updates via git commit + push
+- Natural namespacing via directory structure
+
+**Negative:**
+- Concurrent writes can race (mitigated by concurrency groups in CI workflows)
+- `git worktree` adds complexity to the write path
+- State branch appears in `git branch -a` output (minor clutter)
+- Push failures on the state branch are non-fatal (logged as warning, sync still succeeds)