fix(diagnostics): publish the error shape rather than its text in three logs

[datlechin]

swiftlint lint --strict is red on main right now, so the next v* tag would fail its lint job before it built anything.

Three sites log error.localizedDescription at .public, which the public_error_text_in_log rule rejects at error severity: a driver or Foundation error's text carries row values, paths and server messages.

• MCPRemoteToolCoordinator, when a server does not list its tools
• ExportTreeBuilder, on a failed catalog read and on a database whose tables do not load

Each now publishes error.publicLogShape, which is what every other call site in the app does and what the rule's own message asks for.

Found by a CI audit, not by CI: lint only runs on a release tag today, so nothing reported these on the pull requests that introduced them.

swiftlint lint --strict is clean and the app builds.