feat(api): route elaboration through local LLM when configured

Phase 2 of "local OSS models as agents" plan. Adds a third elaboration
path that calls the local OpenAI-compatible LLM via the internal/llm
client, and reorders dispatch so the cheap path is tried first:
local → claude → gemini, with each next attempt only on hard failure
of the prior.

Wiring is opt-out, not opt-in: when [local_model].endpoint is set,
elaboration prefers local by default. Users with a slow or low-quality
local model can disable just elaboration via:

    [local_model]
    endpoint = "..."
    prefer_for_elaborate = false

without giving up the runner or the classifier path.

Implementation:
- Server gains an optional *llm.Client field via SetLLM (matches the
  existing SetNotifier/SetWorkspaceRoot setter pattern, no NewServer
  signature break).
- elaborateWithLocal() reuses buildElaboratePrompt verbatim and asks
  for response_format=json_object so we skip markdown-fence cleanup.
- handleElaborateTask reorders try chain; existing Claude-first
  behavior is preserved exactly when SetLLM is not called.
- LocalModel.UseForElaborate() encapsulates the default-true gating
  with a *bool so explicit-false survives TOML parse.

Tests:
- elaborateWithLocal: parses valid response, errors on nil client,
  errors on bad JSON.
- handler: local preferred when wired; falls back to claude when
  local fails; unchanged behavior when no LLM is configured.
- config: UseForElaborate gating across empty/default/explicit-true/
  explicit-false cases.

Pre-existing test failures noted in docs/plans/local-oss-runner.md
(post-epic cleanup): TestGeminiLogs_ParsedCorrectly returns 404 for
gemini execution log fetch — predates this change.

Plan: docs/plans/local-oss-runner.md.

https://claude.ai/code/session_017Edeq947TpSm1vQTxMhi1J

0 files changed, 0 insertions, 0 deletions