fix(worktree): address CodeRabbit PR review feedback

- Document --branch override in npx-cli help text
- Guard ContextBuilder against empty projects[] override; fall back to cwd-derived primary
- Ensure merged_into_project indexes are created even if ALTER ran in a prior partial migration
- Reject adopt --branch/--cwd flags with missing or flag-like values
- Use defined --color-border-primary token for merged badge border

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

src/npx-cli/index.ts

@@ -52,7 +52,7 @@ ${pc.bold('Runtime Commands')} (requires Bun, delegates to installed plugin):
   ${pc.cyan('npx claude-mem restart')}              Restart worker service
   ${pc.cyan('npx claude-mem status')}               Show worker status
   ${pc.cyan('npx claude-mem search <query>')}       Search observations
-  ${pc.cyan('npx claude-mem adopt [--dry-run]')}    Stamp merged worktrees into parent project
+  ${pc.cyan('npx claude-mem adopt [--dry-run] [--branch <name>]')}    Stamp merged worktrees into parent project
   ${pc.cyan('npx claude-mem transcript watch')}     Start transcript watcher
 
 ${pc.bold('IDE Identifiers')}: