doctor: report what each draft store holds (readable / markerless / encrypted / unreadable), with --drafts

[renezander030]

What

• capcut doctor adds a draft-store check for every default CapCut/JianYing project directory it finds: how many projects are readable, markerless, encrypted or unreadable. Same classification as the template.store report of init / quickstart / compile.
• On a JianYing 6.0+ store (every app-written project is an encrypted payload) the check is a warning that says what still works: init, quickstart and compile build plaintext drafts from the bundled template; pinning JianYing to 5.9.x keeps app-made projects editable; capcut decrypt <project> for one project; details in docs/jianying-encryption.md.
• New --drafts <dir> inspects one folder instead of the per-OS defaults, so the check runs on a machine without the app and in CI. A missing folder is a warning with a fix hint, not a hard failure.

Why

The encrypted-store situation is the most repeated support question in the JianYing ecosystem and was only surfaced here after a command failed on such a project. Naming it once, up front, with the working path next to it, is cheaper for everyone.

Tests

• test/doctor-store.test.mjs: mixed store (2 encrypted + 1 CLI-made readable), all-encrypted, plaintext, empty, missing folder, and the -H layout.
• Full suite: 981 pass, 0 fail. Biome clean. packaging.test.mjs unchanged: the check uses a structural type so doctor.d.ts pulls no new declarations into the tarball.

Docs

CHANGELOG (Unreleased), command reference (en regenerated, zh by hand), docs/jianying-encryption.md + zh-CN: one bullet each in "What the CLI says on such a store".