0.35: Remodel around dsh trajectory feature.

[MathisWellmann]

• Include system_prompt method in trait EvolutionAgent and use rig from git directly to get access to the system prompt.
• remove system_prompt from DshSessiion as its now in EvolutionTrace
• remove public EvolutionTrace::render method as its not useful.
• Some file and module refactors.
• Add provider method to EvolutionAgent and remove it from DshHeader to instead put it into EvolutionTrace.
• remodel agent_builder_from_env into agent_from_env, remove init_agent_from_env
• remove model from DshSession and put it into EvolutionTrace, wiring it through the EvolutionTrace trait.

[github-actions]

Summary

The PR replaces the Agent type alias with a wrapper struct carrying the provider base URL, moves the system prompt/provider from DshSession into EvolutionTrace, reorganizes inference code into an inference/ module, switches rig to a git dependency, and updates all examples to the new API. One call site was not converted and breaks the build.

Issues

• symbiont/benches/batch_throughput.rs:614-619 — Blocker. agent_from_env now returns a built symbiont::Agent (previously AgentBuilder), but the benchmark still chains .max_tokens(MAX_OUTPUT_TOKENS).build() on that result. Those methods exist only on the rig AgentBuilder; the returned Agent (and the rig_agent::Agent it derefs to) has neither, so the bench target no longer compiles under cargo bench / cargo check --all-targets. Build the agent via symbiont::agent_builder(...) with .max_tokens(MAX_OUTPUT_TOKENS).build() and wrap with Agent::new, as the examples in this same diff do.

[github-actions]

Summary

The PR wraps rig_agent::Agent in a new symbiont::Agent (carrying provider/model), moves provider/model/system prompt into EvolutionTrace, restructures inference* into an inference/ module, and drops the trace's public render/JSONL APIs. Solid direction, but it ships a broken doc test and a silent break of persisted-trace deserialization.

Issues

• symbiont/src/dsh/mod.rs:65 — blocker. The module's no_run example still calls DshSession::builder().provider("openrouter").model("moonshotai/kimi-k3"), but the provider/model/system_prompt fields were removed from DshSession in symbiont/src/dsh/export.rs. Doc tests compile even when no_run, so cargo test --features dsh-export (or --all-features) fails to build; the "Fields the session takes from the caller" bullet list (mod.rs:28) is stale the same way. Remove the two builder calls and reword the bullets to say these fields now come from the trace.
• symbiont/src/evolution_trace.rs:51,55,63 — major. The new provider, model, and system_prompt fields have no #[serde(default)], so Deserialize now rejects every trace persisted by 0.33/0.34, and the serde_round_trip test that guarded "a host can read a persisted trace back for offline analysis" was deleted with no replacement. Add #[serde(default)] to the three fields (and keep a round-trip test) or explicitly document the format break.

[github-actions]

Summary

PR replaces the rig_agent::Agent type alias with a new symbiont::Agent wrapper that records provider URL and model, moves the system prompt/provider/model from DshSession onto EvolutionTrace, restructures inference.rs into an inference/ module (with error classification moved to inference_utils.rs), and switches rig to a git fork. The migration is complete and internally consistent across crate, examples, and tests; remaining findings are a doc/signature mismatch and an untested new code path.

Issues

• symbiont/src/lib.rs (~line 144, also the AgentBuilder alias docs and inference/agent_builder.rs) — Major: the doc comments document Agent::new(built, base_url) with two arguments, but the new constructor takes three (inner, provider, model); copy-pasted examples fail to compile. Fix: show the three-argument form, passing model as well.
• symbiont/src/inference/agent_builder.rs (new test init_agent_carries_the_base_url_as_provider) — Major: the new Agent::system_prompt() path (reading rig's run_spec().preamble, which populates EvolutionTrace.system_prompt and the dsh session header's system field) is untested; the only new unit test asserts provider(). A wrong or empty preamble would make every exported session carry an empty system prompt with no test to catch it. Fix: assert the expected prompt in that test (or against a trace built by the runtime).

[github-actions]

Summary

Bumps symbiont 0.33→0.35: replaces the Agent type alias with a struct that carries provider/model, moves provider/model/system-prompt from DshSession onto EvolutionTrace, derives EvolveInfo::usage() from the trace, and folds inference helpers into a inference/ module. The refactor is internally consistent — all call sites updated, usage-sum equivalence verified, no dangling references to the removed render/write_jsonl/to_json_pretty or the old *_from_env helpers. No functional blocker found.

Issues

• symbiont/src/system_prompt.rs:209 — Major (doc). The system_prompt function still documents that "EvolutionTrace omits the preamble by design," which this diff makes false: it adds system_prompt to EvolutionTrace and records the agent's preamble in every lane. The diff deliberately removed the identical "absent by design / store it beside the traces" note from evolution_trace.rs but left this one, so the user-facing API doc now states the opposite of the new behavior. Fix: update system_prompt.rs to say the trace now records the preamble (or that the free function is for reproducing it independently).

[github-actions]

Summary

The PR replaces the Agent type alias with a wrapper that carries provider/model, moves system prompt/provider/model from DshSession onto EvolutionTrace (with serde(default) back-compat), renames init_agent_from_env/agent_builder_from_env to agent_from_env/init_agent, and consolidates inference code into an inference module. Verified: EvolutionTrace::usage() still sums every attempt that reached the model (matching the removed runtime accumulator), no stale call sites of the removed APIs remain, and the dsh-export feature-gating in the doc test is valid. The remaining problems are public docs that now contradict the new behavior.

Issues

• symbiont/src/system_prompt.rs:210, major — the doc still states EvolutionTrace "omits the preamble by design" and that the caller must fetch system_prompt() separately (the old DshSession contract), but the trace now records the preamble and DshSession no longer accepts it; a host following this doc misreads the export contract. Rewrite the paragraph to say the trace carries the preamble.
• symbiont/src/lib.rs:149, major — the Agent doc shows the two-argument call Agent::new(builder.tool(..).build(), base_url), but Agent::new requires a third model argument, and the AgentBuilder doc (line ~190) repeats "passing the same base_url" without it; a host copy-pasting the documented wrapping step does not compile. Show the three-argument call in both places.