Simplify bench code and consolidate docs for MOQ protocol work

Code: fix histogram/latency API to what callers use, iodata payloads in
the paced sender hot loop, bulk object chunking and batched lock use in
quicprobe, object-delivery normalization moved into the Quicprobe
adapter, validate --object-size >= 8.

Docs: fold docs/agents into AGENTS.md, retire ADRs 0001-0005 into
CONTEXT/README, drop the journey doc and closed tracker issues,
reconcile agent-skills and untrack .agents, trim the moqxprobe README
to commands and contract.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: dmorn