Release 2.2.0 — unified onboard strategy + safety hardening

Folds `josh-sync adopt` into `josh-sync onboard <target>` as the adopt
strategy alongside the original reset flow. Strategy resolves by
precedence: --mode flag > targets[].history_lock config (preserve|rewrite)
> auto-detect via `git ls-remote --heads`. `josh-sync adopt` is kept as
a thin alias. Adds the new `targets[].history_lock` config field
(validated at parse time) and folds `<target>/adopt.json` state into
`<target>/onboard.json` with a `.strategy` field; legacy state files
are read with a backward-compat fallback.

Safety hardening (from a multi-angle review of the unification):
- auto-detect distinguishes auth/network failure from empty repo
- resume validates --mode against the strategy saved in state
- `josh-sync adopt` rejects a conflicting --mode in the forwarded args
- missing import-PR lookup dies in both strategies (was WARN+continue
  for reset, which could create duplicate import PRs on resume)
- --restart durably removes the legacy adopt.json from the state branch
- adopt_branch is now a subshell function (EXIT trap can't clobber callers)
- strategy value validated after resolve/load (reset|adopt)
- --mode with missing/empty value dies with a usage hint
- migrate-pr against an adopt-strategy target dies with a specific hint
- reset importing asserts archived_url is present (no "null" → git clone)

End-to-end + CLI bats coverage added (tests/unit/adopt_e2e.bats,
tests/unit/cli.bats). 72 tests, shellcheck clean.

Makefile dist bundle header now correctly interpolates VERSION and
line count.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/adr/013-non-destructive-adoption.md

@@ -2,6 +2,7 @@
 
 **Status:** Accepted
 **Date:** 2026-04
+**Update (2026-05):** The standalone `josh-sync adopt <target>` command described below has been folded into `josh-sync onboard <target>` as the `adopt` strategy (selectable via `--mode=adopt`, `targets[].history_lock: preserve`, or auto-detection when the subrepo has any branches). `josh-sync adopt` is retained as a thin CLI alias. The state file moved from `<target>/adopt.json` to `<target>/onboard.json` with a `.strategy` field; the legacy file is still read for backward compatibility. See the guide's Onboarding section.
 
 ## Context