docs(hyperguild): document brain pass-rate subcommand and /pass-rate endpoint

Adds pass-rate to the CLI README's subcommand block. Updates CLAUDE.md
to note the new /pass-rate endpoint alongside the existing brain
HTTP REST API surface. Updates the session_log MCP tool's
final_status description to reflect the new pass|fail|skip vocabulary
introduced by Plan 5's SKILL.md instrumentation; the aggregator
still accepts legacy ok|error|skipped values for backwards compat.

ingestion/internal/mcp/handlers.go

@@ -77,7 +77,7 @@ func (s *Server) tools() []map[string]any {
 				"skill":        str("skill name"),
 				"phase":        str("phase within the skill"),
 				"project_root": str("absolute project root"),
-				"final_status": str("ok | error | skipped"),
+				"final_status": str("pass | fail | skip (legacy: ok | error | skipped also accepted)"),
 				"file_path":    str("optional file produced"),
 				"model_used":   str("optional model identifier"),
 				"duration_ms":  int_("optional duration in ms"),