feat(20-01): add tod-mib-parser Go CLI binary

- Add gosmi v1.0.4 dependency for MIB parsing
- Create poller/cmd/mib-parser/ with main.go and tree.go
- CLI accepts MIB file path and optional --search-path
- Outputs JSON OID tree with oid, name, description, type, access, status, children
- Errors output as JSON {"error":"..."} to stdout (exit 0) for Python backend
- Panic recovery wraps gosmi LoadModule for malformed MIBs
- Parent-child tree built from OID hierarchy with numeric sort

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

poller/go.mod

@@ -28,6 +28,7 @@ require (
 	dario.cat/mergo v1.0.2 // indirect
 	github.com/Azure/go-ansiterm v0.0.0-20230124172434-306776ec8161 // indirect
 	github.com/Microsoft/go-winio v0.6.2 // indirect
+	github.com/alecthomas/participle v0.4.1 // indirect
 	github.com/antithesishq/antithesis-sdk-go v0.6.0-default-no-op // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cenkalti/backoff/v4 v4.3.0 // indirect
@@ -73,6 +74,7 @@ require (
 	github.com/nats-io/nuid v1.0.1 // indirect
 	github.com/opencontainers/go-digest v1.0.0 // indirect
 	github.com/opencontainers/image-spec v1.1.1 // indirect
+	github.com/opsbl/gosmi v1.0.4 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/power-devops/perfstat v0.0.0-20210106213030-5aafc221ea8c // indirect