…iteral capture

RL runs many opencode trials concurrently against one served vLLM behind a
single shared RecordProxy, so their captured completions interleave in one log.
Content correlation (datagen's literal_correlator) cannot disambiguate GRPO
groups (n>1 rollouts of the IDENTICAL prompt -> every continuation ambiguous).

Add a per-trial correlation id transported as an HTTP header (confirmed to
forward through opencode-ai 1.18.2 @ai-sdk/openai-compatible options.headers):
- opencode.py mints a per-trial id when collect_rollout_details is on, stamps it
  into the vllm provider options.headers[x-ot-trial-id], and surfaces it on
  context.metadata[rollout_correlation_id] for the RL-loop glue.
- RecordProxy captures the x-ot-trial-id request header onto each JSONL entry
  (trial_id) on both the streaming and non-streaming paths.
- new harbor.literal.rollout_build: build_rollout_details_from_pairs (the shared
  Chat.rollout_details-mirroring parity builder, extracted from opencode.py) and
  build_rollout_details_for_trial (filter a shared log by trial_id, order by
  arrival -> one RolloutDetail; spans opencode auto-compaction boundaries).

Flag off => no id, no header, no metadata, trial_id=None (byte-identical;
datagen/content path untouched). Tests: n>1 identical-seed no-bleed, compaction
ordering, header round-trip, parity guard. 83 harbor unit tests green.

…teral-bridge header

The per-trial correlation-id header forwards through @ai-sdk/openai-compatible on
opencode-ai 1.18.2 (older 1.0.x dropped provider options, opencode #5674). RL runs
relying on the literal bridge must pin version 1.18.2 in the agent config. Comment
only; no behavior change.

…er (RL literal bridge GAP C)

The RL rollout generator forces model_name="hosted_vllm/<alias>"
(terminal_bench_generator), but the baseURL/apiKey/@ai-sdk/openai-compatible +
x-ot-trial-id correlation-header branch was gated on provider=="vllm" only, so it
never fired for opencode-in-RL: opencode got no baseURL and no per-trial header, the
shared RecordProxy could not attribute its log entries, and correlation no-op'd. Treat
"hosted_vllm" like "vllm" in the config-writer AND the two downstream env-selection
gates in run() (OPENAI_API_KEY/OPENAI_BASE_URL keys + the OPENCODE_DUMMY_KEY injection).

Adds real-path tests over the actual config-writer under model_name="hosted_vllm/..."
(header + npm + baseURL), byte-identical flag-off, and version/opencode_config reaching
the ctor. The prior header test used "vllm/..." so it passed while the real path no-op'd.

…(not OPENAI_BASE_URL)

_build_register_config_command sourced the self-hosted vLLM baseURL from
OPENAI_BASE_URL. That var is RESERVED for genuine OpenAI traffic — the LLM-judge
verifiers on the worker read it — so having the RL runner publish the vLLM
capability URL there silently misroutes every judge call to vLLM. Prefer the
harbor-specific HARBOR_MODEL_ENDPOINT (the var the RL runner already publishes for
the co-located served model); keep OPENAI_BASE_URL as a back-compat fallback so
nothing else regresses. Also forward HARBOR_MODEL_ENDPOINT into the sandbox env for
the vllm/openai providers, symmetric with the baseURL source (non-load-bearing: the
baseURL is baked into opencode.json). Adds 2 tests (prefers HARBOR_MODEL_ENDPOINT;
falls back to OPENAI_BASE_URL); 51 opencode tests pass.