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>

Makefile

@@ -19,7 +19,7 @@ dist/josh-sync: bin/josh-sync lib/*.sh VERSION
 	@mkdir -p dist
 	@echo "Bundling josh-sync..."
 	@echo '#!/usr/bin/env bash' > dist/josh-sync
-	@echo "# josh-sync $(cat VERSION) — bundled distribution" >> dist/josh-sync
+	@echo "# josh-sync $$(cat VERSION) — bundled distribution" >> dist/josh-sync
 	@echo '# Generated by: make build' >> dist/josh-sync
 	@echo '' >> dist/josh-sync
 	@# Inline all library modules (strip shebangs and source directives)
@@ -36,7 +36,7 @@ dist/josh-sync: bin/josh-sync lib/*.sh VERSION
 		| sed '/^JOSH_LIB_DIR=/,/^source/d' \
 		>> dist/josh-sync
 	@chmod +x dist/josh-sync
-	@echo "Built: dist/josh-sync ($(wc -l < dist/josh-sync) lines)"
+	@echo "Built: dist/josh-sync ($$(wc -l < dist/josh-sync) lines)"
 
 clean:
 	rm -rf dist/