v1.108.153 — tool_surface schema receipt in get_session_stats

get_session_stats now carries an advisory tool_surface block: visible-vs-catalog tool counts, estimated schema tokens for each, schema_tokens_avoided by the active surface/tier (Counter or a narrow profile), and the top-15 heaviest schemas. Counted at the meter's bytes/4 scale over the same {name, description, inputSchema} serialization the CI schema-budget guardrail uses, so the runtime receipt and the regression gate agree by construction.

Read-only, computed inline on the stats call only, nothing persisted; a probe failure omits the block rather than failing the call. No new tool, no schema change, no INDEX_VERSION change.