rpc: raise default HTTP threads to 16

[MikeGarciaAGM]

Raise the default RPC thread count from 4 to 16 and align the reduce-memory docs with the new default.\n\nThis keeps the change small and reviewable while matching the documented intent of the lane.

[MikeGarciaAGM]

Quick status ping on this PR:

• Still open and mergeable-clean from my side.
• It remains one of the stronger Bitgesell lanes in the current ranking.
• I am keeping it concise and ready in case maintainers want a quick review pass.

[MikeGarciaAGM]

Quick status ping: this PR is still open and mergeable-clean. The change remains tight and focused on the HTTP thread default plus the matching docs, so if this is still a good bounty path, I'm ready to make the smallest possible follow-up quickly.

[MikeGarciaAGM]

Quick refresh: this PR is still open and mergeable-clean on my side. The scope remains tight and focused on the HTTP thread default plus the matching docs, so if this is still a valid bounty path, I'm ready to apply any tiny follow-up you want quickly.

[MikeGarciaAGM]

Quick review ping: PR #335 is still open and mergeable-clean on my side. The scope remains tight to raising the default HTTP threads plus matching docs, so it should be easy to review quickly. If this is still an active bounty path, I'd appreciate a maintainer look when convenient. @janus @van-orton

[MikeGarciaAGM]

Quick status update: this PR is still open, mergeable, and currently has no external review requests. The change remains focused on raising the default RPC thread count to 16 and aligning the docs. If you have a moment, a quick review would help move it toward merge.