Add typed trace destinations for session imports

[Stephen Belanger (Qard)]

Summary

• add typed project-log, experiment, and exported-parent destinations to the daemon wire contract
• accept project_logs:<project-id>, experiment:<experiment-id>, or --parent <SpanComponents> on imports
• preserve parent object routing, external trace roots, and propagated events in the Braintrust sink
• retain legacy project, experiment metadata, and parent/root fields as fallback

Covers SDK-130.

Validation

• cargo test --manifest-path bt-daemon/Cargo.toml --all-features --locked
• cargo clippy --manifest-path bt-daemon/Cargo.toml --all-targets --all-features --locked -- -D warnings
• standalone import help smoke test

[Copilot]

Pull request overview

Adds a typed destination field to the bt-daemon wire SessionConfig so session imports (and other front-ends) can route traces explicitly to project logs, an experiment, or under an exported parent span, while keeping legacy routing fields as a fallback.

Changes:

• Introduce TraceDestination in the wire contract and plumb it through redaction/journaling.
• Update translators + Braintrust sink routing so exported-parent destinations preserve object routing, external roots, and propagated events.
• Extend tests/docs to validate typed destinations and precedence over legacy metadata.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
bt-daemon/tests/pipeline.rs	Updates SessionConfig literals for the new destination field.
bt-daemon/tests/codex_translator.rs	Updates configured test context to include destination.
bt-daemon/tests/braintrust_sink.rs	Adds coverage for exported-parent propagation and typed experiment routing precedence.
bt-daemon/src/wire/mod.rs	Re-exports TraceDestination from the wire module.
bt-daemon/src/wire/envelope.rs	Adds SessionConfig.destination, defines TraceDestination, implements parsing + attached-span helpers, includes in redaction.
bt-daemon/src/translate/codex.rs	Shapes emitted root rows to attach under an external parent span when provided.
bt-daemon/src/translate/claude.rs	Uses typed destination-derived parent/root ids via attached_span_ids().
bt-daemon/src/sink/braintrust.rs	Implements typed destination routing (project logs / experiment / parent span), including propagated event handling.
bt-daemon/src/main.rs	Updates standalone CLI config construction to include destination: None.
bt-daemon/src/lib.rs	Extends import CLI args with typed destination / --parent and applies them to session config.
bt-daemon/src/journal.rs	Restores destination when reconstructing config from redacted journal entries.
bt-daemon/docs/protocol.md	Documents the new destination field and import CLI syntax.

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