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>

lib/sync.sh

@@ -265,6 +265,8 @@ reverse_sync() {
   fi
 
   # 4. Find new human commits (excludes bot commits from forward sync)
+  #    Uses --ancestry-path to restrict to the direct lineage and avoid
+  #    leaking old history through reconciliation merge parents.
   local human_commits
   human_commits=$(git log --ancestry-path "mono-filtered/${mono_branch}..HEAD" \
     --oneline --invert-grep --grep="^${BOT_TRAILER}:" 2>/dev/null || echo "")
@@ -278,7 +280,7 @@ reverse_sync() {
   log "INFO" "New human commits to sync:"
   echo "$human_commits" >&2
 
-  # 4. Push through josh to a staging branch
+  # 5. Push through josh to a staging branch
   local ts
   ts=$(date +%Y%m%d-%H%M%S)
   local staging_branch="auto-sync/subrepo-${subrepo_branch}-${ts}"
@@ -286,7 +288,7 @@ reverse_sync() {
   if git push -o "base=${mono_branch}" "$(josh_auth_url)" "HEAD:refs/heads/${staging_branch}"; then
     log "INFO" "Pushed to staging branch via josh: ${staging_branch}"
 
-    # 5. Create PR on monorepo (NEVER direct push)
+    # 6. Create PR on monorepo (NEVER direct push)
     local pr_body
     pr_body="## Subrepo changes