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

1 files changed, 30 insertions, 0 deletions

diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index 2bba2c4..e4f1a5d 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -53,3 +53,33 @@ func TestLoadFile_MissingFile_ReturnsError(t *testing.T) {
 		t.Fatal("expected error for missing file, got nil")
 	}
 }
+
+func TestLocalModel_UseForElaborate_EmptyEndpoint(t *testing.T) {
+	m := LocalModel{}
+	if m.UseForElaborate() {
+		t.Error("empty endpoint should never opt into elaborate")
+	}
+}
+
+func TestLocalModel_UseForElaborate_DefaultTrue(t *testing.T) {
+	m := LocalModel{Endpoint: "http://localhost:11434/v1"}
+	if !m.UseForElaborate() {
+		t.Error("endpoint set + default flag should opt in")
+	}
+}
+
+func TestLocalModel_UseForElaborate_ExplicitFalse(t *testing.T) {
+	f := false
+	m := LocalModel{Endpoint: "http://localhost:11434/v1", PreferForElaborate: &f}
+	if m.UseForElaborate() {
+		t.Error("explicit false should opt out")
+	}
+}
+
+func TestLocalModel_UseForElaborate_ExplicitTrue(t *testing.T) {
+	tr := true
+	m := LocalModel{Endpoint: "http://localhost:11434/v1", PreferForElaborate: &tr}
+	if !m.UseForElaborate() {
+		t.Error("explicit true should opt in")
+	}
+}