test(persist): interactive run without --ephemeral creates .harness/<agent>/ persistence dir

[hggz]

What

Adds an e2e test that locks the boundary in the interactive + non-ephemeral branch of run():

• TTY (no -p, no piped stdin)
• no --ephemeral flag

In that branch the CLI is required to materialize the persistence dirs that the active adapter advertises via persistMounts() and pass them as -v mounts. For the pi adapter that means creating <cwd>/.harness/pi/ and emitting a -v <host>:/home/harness/.pi/agent mount.

Why

This is the inverse of the two existing implicit-ephemeral tests (-p and piped stdin) — both assert that .harness/ is not created. Nothing currently asserts the positive case, so a future refactor that flips effectiveEphemeral or drops the fs.mkdirSync() call would slip through CI.

The branch is only reachable when process.stdin.isTTY === true, so the test allocates a PTY via util-linux script (same approach as the existing pi: interactive ... no -p test merged in #5/#22). Self-skips on platforms without script.

How verified

pnpm install --frozen-lockfile && pnpm build && pnpm test:e2e:cli
# 21/21 pass (was 20/20)
pnpm lint:ts
# Checked 6 files. No fixes applied.

Net diff: +1 test in tests/e2e/cli.test.mjs.