Chronicle: per-subcommand telemetry attribution for sessionStoreSql tool (#319054)

chronicle: per-subcommand telemetry attribution for sessionStoreSql tool

Add a 'subcommand' enum input on copilot_sessionStoreSql so each /chronicle slash command (standup, tips, cost-tips, search, improve, reindex) tags its tool calls. Plumb it through _invokeQuery/_invokeStandup/_invokeReindex and emit it on the chronicle.sqlQuery telemetry event (with 'unknown' for ad-hoc model calls). Also add command/target/success dimensions while preserving the legacy 'source' value so existing dashboards keep working. Update each chronicle-*.prompt.md to instruct the model to set the subcommand on every call.