`MCP: registered N tool(s) from M server(s) (2 failed)` left the failing
identity diagnosable only by elimination from the per-server `registered`
lines. The per-server WARNING fires only on the immediate-failure path; a
candidate skipped for its retry cooldown (a failure from an earlier pass) is
counted as failed with no line of its own at all.
`_connected_summary` now returns `(name, reason)` pairs and `_log_summary`
prints them inline: `(2 failed: github (Connection closed); notion (HTTP 401
...))`. The reason is the recorded `_server_connect_errors` entry (already
credential-scrubbed by `_format_connect_error`); a candidate never attempted
this pass reads `not attempted (in retry cooldown)`. One line, no second
WARNING per server on the path that already warns.
Slimmer redo of #114794 (@liuhao1024, earliest) and #114872 (@Finn763): both
name the failures via an extra WARNING per server; inline on the summary keeps
the immediate-failure path at its current two WARNINGs and still covers the
cooldown case. #114872's extra `_sanitize_error` pass is redundant with the
recorder.
Fixes#114746
Co-authored-by: liuhao1024 <sunsky.lau@gmail.com>
Co-authored-by: finn763 <165816600+finn763@users.noreply.github.com>
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