feat: add migrate-v2.sh — standalone v1 → v2 migration script

New entry point: `bash migrate-v2.sh` from the v2 checkout.
Replaces the old setup-embedded migration flow with a standalone
4-phase script + rewritten Claude skill for the interactive parts.

Phase 0: Bootstrap (Node/pnpm/deps via setup.sh) + find v1
Phase 1: Core state (env, DB, groups, sessions, tasks)
Phase 2: Channels (clack multiselect, auth copy, code install)
Phase 3: Infrastructure (OneCLI, auth, Docker, skills, container build)
Service switchover: stop v1 → start v2 → test → keep or revert
Phase 4: Handoff → exec claude "/migrate-from-v1"

The skill handles: owner seeding, access policy, CLAUDE.local.md
cleanup, container config validation, fork customization porting.

Key fixes found during testing:
- triggerToEngage: requires_trigger=0 must override non-empty pattern
- unknown_sender_policy defaults to 'public' (strict drops all msgs
  before owner is seeded)
- Service revert must stop v2 (parse unit name from step log, not
  early tsx one-liner that can fail)
- Session continuity: copy JSONL from -workspace-group/ to
  -workspace-agent/ and write continuation:claude into outbound.db
- container_config.additionalMounts written directly to container.json
  (same shape in v1 and v2)
- EXIT trap writes handoff.json; explicit write_handoff before exec

Includes migrate-v2-reset.sh for dev iteration and docs/migration-dev.md
for testing/debugging reference.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

setup/migrate-v1/shared.ts

@@ -431,12 +431,14 @@ export function triggerToEngage(input: {
   if (pattern === '.' || pattern === '.*') {
     return { engage_mode: 'pattern', engage_pattern: '.' };
   }
-  if (pattern) {
-    return { engage_mode: 'pattern', engage_pattern: pattern };
-  }
+  // requires_trigger=0 means "respond to everything" regardless of pattern.
+  // The pattern was used for mention highlighting, not message gating.
   if (!requiresTrigger) {
     return { engage_mode: 'pattern', engage_pattern: '.' };
   }
+  if (pattern) {
+    return { engage_mode: 'pattern', engage_pattern: pattern };
+  }
   return { engage_mode: 'mention', engage_pattern: null };
 }