feat: export single envvar span during pre app start

[sohankshirsagar]

• Creates single env var span that CLI uses to set env vars in environment before replaying tests (only if enabled in .tusk/config.yaml

• remove old env var code

• should be merged/deployed along with feat: replay tests grouped by environment and set envvars before starting server tusk-drift-cli#54

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Note

Create a single pre-app-start env vars snapshot span (when enabled) and remove all old env var recording/replay logic; propagate environment through spans and exporters.

• Core:
  • Add pre-app-start ENV_VARS_SNAPSHOT span in TuskDriftCore (RECORD mode, gated by recording.enable_env_var_recording).
  • Expose getEnvironment() and pass environment into span creation and mock requests.
  • Remove sync env-var request logic from TuskDrift and ProtobufCommunicator.
• Tracing/Export:
  • Include optional environment in CleanSpanData, SpanTransformer, TdSpanExporter, and API export (ApiSpanAdapter), defaulting to empty string on wire.
  • Accept outputValue and generic metadata objects in span utils/transformer APIs.
• Instrumentations:
  • HTTP/Next.js: remove CLI env-var fetching and metadata usage; include environment on inbound replay spans sent to CLI.
  • Delete env var instrumentation and tracker: instrumentation/libraries/env/**, EnvVarTracker.
• ProtobufCommunicator:
  • Drop env-var message handling and helper; simplify sync request file prefix docs.
• Types:
  • Remove MetadataObject type; use Record<string, unknown>; add environment?: string to CleanSpanData.
• Dependencies:
  • Bump @use-tusk/drift-schemas to ^0.1.19.

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