socket client now retries connect/IO failures with 2-4-8-16-30s
backoffs (60s total budget). transparent for non-tool callers via
request(); tool handlers go through request_retried() which also
returns the retry count, then annotate_retries() appends a one-line
note to the tool result so claude knows the slow round-trip was a
c0re flicker, not a content failure — avoids burning tokens on an
LLM-level retry.
