Migrate tracing from jaeger-client to OpenTelemetry

Problem

The jaeger-client Python library is archived and incompatible with Python 3.12 (its dependency chain crashes with AttributeError due to removed collections.MutableMapping).

Solution

Migrate the tracing subsystem from the archived jaeger-client to the OpenTelemetry SDK with OTLP gRPC exporter, which is the officially recommended replacement.

Changes

• Replace jaeger_client import with opentelemetry SDK packages in gluetool/action.py
• Rewrite Tracer to use TracerProvider + OTLPSpanExporter
• Replace GLUETOOL_TRACING_REPORTING_HOST / GLUETOOL_TRACING_REPORTING_PORT env vars with single GLUETOOL_TRACING_REPORTING_ENDPOINT (default http://localhost:4317)
• Update Action span API: finish() → end(), set_tag() → set_attribute(), child_of → context
• Simplify Tracer.close() to use provider.force_flush() + shutdown()
• Add opentelemetry-sdk and opentelemetry-exporter-otlp-proto-grpc as dev dependencies
• Remove jaeger_client section from mypy.ini
• Update logger handling in gluetool/log.py from jaeger_tracing to opentelemetry

Companion MR

• gluetool-modules!1042 — replaces jaeger-client dependency with OpenTelemetry packages

Assisted-by: Claude Code