Expose the telemetry stats surface

Give the telemetry stats reads a subject, so a caller can ask for them. The database part already computes the statistics: `read_hourly_stats`, `read_daily_stats`, `get_summary` and `read_by_session` read the four aggregate functions in projects/ores.sql/create/telemetry/telemetry_stats_functions_create.sql, and the component's tests exercise them. Nothing can ask for the result, because the component's six subjects carry logs, service samples and NATS samples only.

The clean standard's B06 classifies every public symbol by its consumer and says a test is not a consumer: a symbol reached only from a test is dead code, and the task either names its intended consumer or deletes it. These four reads are exactly that case, and the intended consumer is the observability view that should render them.

Exposing them is a model change, not a clean-up: it needs the query and result shapes modelled, a subject per read, the handler wired, and the generated protocol header in place of the hand-written call path. That is the same shape as the three surfaces this component's clean-up added, so the pattern is established.

`ores.telemetry` reached the standard with these four reads recorded here as their intended consumer, rather than deleted, because the SQL they read stays and deleting the readers would strand a working aggregation.

• projects/ores.telemetry/database/include/ores.telemetry.database/repository/telemetry_repository.hpp — the four reads.
• projects/ores.sql/create/telemetry/telemetry_stats_functions_create.sql — the aggregate functions they read.
• doc/agile/versions/v0/sprint_26/clean-telemetry/evidence/b06_symbol_census.tsv — the census that classified them.

• Generate messaging registrars via codegen — the registrar this surface would join.