v0.6.8 — channel digest telemetry
Adds channel_context_op digest telemetry for raw_window+digest channel awareness: digest status, raw vs digest bytes, digest block count, coverage gaps, and deterministic_only, plus a raw/digest byte split in feed-injection budget telemetry. Header parsing stays first-line-only, so the new [digest] body is never mis-parsed as metadata. Telemetry-only — digest injection behavior is unchanged. Refs mostlydev/clawdapus#267 mostlydev/clawdapus#262.