feat(core): anchor agent-created schedules in the user's .cline schedules home (#13634)

* feat(core): anchor agent-created schedules in the user's .cline schedules home

Agent-created schedules inherited whichever workspace folder the chat
session happened to run in, scattering user-level routines across chat
and project folders. They were invisible to workspace-scoped listings
elsewhere, tied to folders that may be cleaned up, and each chat's
tasks tool saw a different set when checking for duplicates.

Anchor them in ~/.cline/schedules instead: the hub's scheduled-task
session defaults now resolve to that home (created on demand), so
agent-created schedules live and run in one stable user-level scope.
The tasks tool guidance now tells agents that scheduled sessions run in
the schedules home, so prompts must carry absolute paths to any project
they operate on.

Schedules created explicitly with a workspace (CLI --workspace, desktop
routine wizard) are unchanged, and existing rows keep their current
workspaceRoot - they stay visible through the all-workspaces listing
paths (#13613, #13633).

* test(core): restore any pre-existing CLINE_DIR after the agenda hub test

The test's cleanup deleted CLINE_DIR outright, so an environment that
had it configured would leave later tests in the same worker on the
default storage directory. Save the previous value and restore it.

* test(core): restore CLINE_DIR even when hub test setup throws early

Restoring the override in the try/finally missed failures thrown during
transport construction or start(), before the try was entered. Register
the restore with onTestFinished instead, which runs regardless of where
the test fails.