Add elapsed run time, per-account results CSV, and a default config path

Summaries now show elapsed wall-clock time since the run started, and every
summary (interim and final) overwrites a results.csv (Object ID, UPN,
persona/status) next to the audit log, so an operator has a plain export
without parsing NDJSON. ConfigPath also now defaults to
./config/persona-engine.json instead of requiring -ConfigPath every run.

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

docs/Logging.md

@@ -38,6 +38,19 @@ warning, **once** per run, and processing continues.
 Once, not once per user: a run over five thousand accounts with a locked log file should warn once,
 or the warning that matters is buried in the noise it generates.
 
+## Results CSV
+
+Alongside the NDJSON audit log, every summary — interim and final — (re)writes a plain CSV listing
+every account processed so far: `AccountObjectId`, `UserPrincipalName`, `PersonaStatus` (the assigned
+persona for `Matched` accounts, otherwise `Unclassified` or `EvaluationError`). It is overwritten in
+full each time, not appended, so it always reflects the whole run to that point rather than only the
+accounts since the last summary.
+
+It is written next to the audit log — same directory as `logging.path` — under `logging.resultsFileName`
+(default `results.csv`). Export failure never ends a run, for the same reason a sink failure doesn't:
+a locked file or full disk is an operational problem, not a reason to abandon a classification run
+mid-population.
+
 ## Record types
 
 | Type | When | Carries |