fix(lemmyv0,piefed): listPersonContent now honors caller-supplied sort

[aeharding]

Summary

listPersonContent in the lemmyv0 and piefed adapters was hardcoding sort: "New" after spreading the caller's payload, so any sort the caller passed was silently clobbered. v1 was already correct.

-  { ...compat.fromPageParams(payload), sort: "New" }
+  { sort: "New", ...compat.fromPageParams(payload) }

Default behavior preserved (still falls back to "New" when caller omits sort); caller's choice now wins.

How it slipped through: the original "fix: sort by new for listPersonContent" (c12912f, Dec 2025) was a one-line change with no test, and no downstream caller validated the wire shape.

Test plan

Adds test/listPersonContent-sort.test.ts — 4 cases covering both providers:

• v0: caller's sort: "Hot" reaches getPersonDetails wire as sort=Hot
• v0: caller omits sort → wire is sort=New
• piefed: caller's sort: "TopWeek" reaches /post/list
• piefed: caller's sort: "Hot" reaches /comment/list

Verified the new tests fail against main (without the fix) and pass with it. All 23 tests pass overall.