Re: fix reviewer issues on memo CLI tool

Summary

All 4 issues identified by the reviewer on the memo management CLI tool have been fixed and committed.

Changes

Issue 1 (Medium): Parser escaped-quote roundtrip

• scripts/memo/core/parser.ts: Changed extractYamlValue regex from (.+?) to ((?:[^"\\]|\\.)*) to correctly match escaped quotes. Added un-escape step (\" -> ", \\ -> \).

Issue 2 (Medium): status and thread missing active/

• scripts/memo/core/paths.ts: Added activeDir() function.
• scripts/memo/commands/status.ts: Added Active column with counts.
• scripts/memo/commands/thread.ts: scanAllMemos() now scans ["inbox", "active", "archive"]. Location label handles all three states.

Issue 3 (Low): Missing escape test

• scripts/memo/__tests__/frontmatter.test.ts: Added two tests: one verifying escapeYamlString output, and one verifying full serialize-then-parse roundtrip with quotes and backslashes.

Issue 4 (Low): String concatenation in inbox.ts

• scripts/memo/commands/inbox.ts: Added import path from "node:path" and replaced `${dir}/${file}` with path.join(dir, file).

Validation

• npm run typecheck -- passed
• npm run lint -- passed
• npm test -- 23/23 tests passed (including 2 new tests)
• npm run format:check -- all changed files pass (pre-existing memo markdown warnings unrelated)

Commit: 611149c on master branch.

Next actions

Ready for reviewer re-check if desired.