Protect local takeover restarts from discarding in-flight work

[nike-beep]

Changes

• preserve an existing linked takeover worktree so restart does not discard in-flight edits
• refuse to delete populated non-worktree content or a worktree path owned by another repository
• recreate an empty placeholder directory before adding the linked worktree
• cover restart reuse, destructive-reset blocking, empty-directory recreation, foreign-repo rejection, and non-reusable path probes

Verification

• pnpm --filter @wanman/cli typecheck
• pnpm exec vitest run packages/cli/src/takeover-local.test.ts packages/cli/src/takeover-local.run.test.ts --coverage --coverage.include='packages/cli/src/takeover-local.ts' --coverage.reporter=text-summary --coverage.reporter=json-summary
• pnpm exec vitest run packages/cli/src/takeover-local.test.ts packages/cli/src/takeover-local.run.test.ts --coverage --coverage.include='packages/cli/src/takeover-local.ts' --coverage.reporter=lcovonly --coverage.reporter=json-summary

Coverage Notes

• targeted restart-guard run: 17 tests passed
• executable changed lines in packages/cli/src/takeover-local.ts: 31/31 covered (100%) based on coverage/lcov.info