Issue Summary

The comment guarding the block_lock / blockqh initialization in src/conn/conn_handle.c is now stale and misleading. It reads:

/\*
 \* Block manager. XXX If there's ever a second block manager, we'll want to make this more
 \* opaque, but for now this is simpler.
 \*/

Both a local block manager (src/block/) and a disaggregated block manager (src/block_disagg/) now coexist and share the same conn->block_lock spinlock and conn->blockqh / conn->blockhash structures. The condition the XXX was waiting for has arrived.

Context

* File: src/conn/conn_handle.c, around line 68
* Why it was written: at the time only one block manager existed; the comment was a forward-looking note to revisit the design if a second one was added.
* Current state: WT_BLOCK_DISAGG intentionally mirrors the first fields of WT_BLOCK (shared-prefix layout), allowing both types to be inserted into the same blockqh / blockhash queues under the same block_lock. This is enforced by static asserts in src/include/verify_build.h.
* Risk of leaving it: the XXX implies the current design is a temporary shortcut that needs reworking, which is no longer true. It misleads future readers into thinking a refactor is still required.

Proposed Solution

* Remove the XXX block comment entirely.
* Replace with a concise, accurate comment explaining that block_lock and blockqh are intentionally shared across all block manager implementations (local and disaggregated).
* Suggested replacement:

/\* Block manager list and lock; shared by local and disaggregated block manager implementations. \*/

Definition of done: stale XXX comment removed, accurate replacement comment in place, s_all passes cleanly.