Cover task moves with tests and verify the required parameter #246

Test coverage for #243. Depends on #244 and #245.

Existing calls to adjust

task_update gains a required parameter, so these break: HttpTests.cs:313, :381, :387, :403. Pass the current parent explicitly rather than null, so the tests document the echo-it-back contract instead of silently unparenting.

New coverage

• move a top-level task under a parent; move a subtask to top level with null; move a subtask from one parent to another
• reject: self-parent, a descendant as parent (the cycle case), a closed parent, a parent from another project
• task_patch with only parentTaskNumber is a real change, not a no-op, and bumps the version
• a stale version still fails on a move
• the response of both tools carries the new parentTaskNumber, not the old one
• a caller without project write access cannot move a task

Schema check

Extend the discovery test so task_update lists parentTaskNumber in its inputSchema.required — that property is the whole point of the design and nothing else pins it.