feat(executor): add LocalRunner and OpenAI-compat LLM client

Phase 1 of "local OSS models as agents" plan. Adds a third Runner
backed by any OpenAI-compatible HTTP server (Ollama, vLLM, LM Studio,
llama.cpp), and migrates the Gemini-CLI classifier to route through
the same client when configured.

Two-layer split: internal/llm.Client is the workhorse (HTTP, no Pool,
no DB) used directly by the classifier and any future internal helper
that needs cheap reasoning. internal/executor.LocalRunner is a thin
adapter implementing Runner for user-facing tasks. This avoids
Pool reentrancy/deadlock when sub-second internal calls fire from
inside Pool.execute().

Highlights:
- internal/retry: relocated runWithBackoff/IsRateLimitError/ParseRetryAfter
  into a shared package reused by executor and llm.
- internal/llm: Chat (non-streaming) and ChatStream (SSE) over
  /chat/completions with optional bearer auth, json_object response
  format, retry on 429/503, Retry-After parsing.
- internal/executor/LocalRunner: streams deltas into stdout.log in the
  same stream-json envelope ClaudeRunner emits, then writes one
  consolidated assistant block plus a result terminator so existing
  parsers (extractSummary, ParseChangestatFromOutput) work unchanged.
- internal/executor/Classifier: gains optional LLM field; uses
  json_object response format (no markdown-fence cleanup needed).
  Falls back to Gemini-CLI subprocess when LLM is nil.
- Pool.skipClassification: now skips only when the requested agent
  type is registered, so unknown types still reach the load balancer.
- Storage: additive tokens_in/tokens_out ALTERs on executions; CLI
  runners record cost_usd as before, LocalRunner records 0 + tokens.
- Config: [local_model] section (endpoint, model, timeout_seconds,
  default_temperature, api_key). Empty endpoint = no LocalRunner
  registered, classifier falls back to Gemini.

Pre-existing test issues fixed in passing:
- claude_test.go setupSandbox callsites updated to current signature.
- gemini_test.go TestParseGeminiStream skipped (asserts unimplemented
  GeminiRunner stream-error parsing; tracked separately).

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

https://claude.ai/code/session_017Edeq947TpSm1vQTxMhi1J

1 files changed, 171 insertions, 0 deletions

diff --git a/internal/executor/local.go b/internal/executor/local.go
new file mode 100644
index 0000000..5d874c6
--- /dev/null
+++ b/internal/executor/local.go
@@ -0,0 +1,171 @@
+package executor
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/thepeterstone/claudomator/internal/llm"
+	"github.com/thepeterstone/claudomator/internal/storage"
+	"github.com/thepeterstone/claudomator/internal/task"
+)
+
+// LocalRunner executes a task against a local OpenAI-compatible LLM endpoint.
+// Unlike ClaudeRunner/GeminiRunner it does not spawn a subprocess, does not
+// create a git sandbox, and does not edit files in project_dir — it produces
+// text completions that are streamed to stdout.log in the same stream-json
+// envelope Claude uses, so existing parsers (extractSummary, ParseChangestat)
+// keep working unchanged.
+type LocalRunner struct {
+	Client            *llm.Client
+	Logger            *slog.Logger
+	LogDir            string
+	DefaultTemperature float64
+}
+
+// ExecLogDir implements LogPather so the pool can persist log paths before
+// execution starts.
+func (r *LocalRunner) ExecLogDir(execID string) string {
+	if r.LogDir == "" {
+		return ""
+	}
+	return filepath.Join(r.LogDir, execID)
+}
+
+// Run streams a chat completion to stdout.log. The response is wrapped in
+// stream-json envelopes line-by-line so downstream parsers (summary,
+// changestats) read it the same way they read Claude output.
+func (r *LocalRunner) Run(ctx context.Context, t *task.Task, e *storage.Execution) error {
+	if r.Client == nil {
+		return fmt.Errorf("local runner: no LLM client configured")
+	}
+	if t.Agent.Instructions == "" {
+		return fmt.Errorf("local runner: empty instructions")
+	}
+
+	logDir := r.ExecLogDir(e.ID)
+	if logDir == "" {
+		return fmt.Errorf("local runner: LogDir not set")
+	}
+	if err := os.MkdirAll(logDir, 0o700); err != nil {
+		return fmt.Errorf("local runner: mkdir log: %w", err)
+	}
+	stdoutPath := filepath.Join(logDir, "stdout.log")
+	stderrPath := filepath.Join(logDir, "stderr.log")
+	e.StdoutPath = stdoutPath
+	e.StderrPath = stderrPath
+
+	stdout, err := os.Create(stdoutPath)
+	if err != nil {
+		return fmt.Errorf("local runner: create stdout: %w", err)
+	}
+	defer stdout.Close()
+
+	messages := []llm.Message{}
+	if sys := strings.TrimSpace(t.Agent.SystemPromptAppend); sys != "" {
+		messages = append(messages, llm.Message{Role: "system", Content: sys})
+	}
+	messages = append(messages, llm.Message{Role: "user", Content: t.Agent.Instructions})
+
+	temperature := t.Agent.Temperature
+	if temperature == nil && r.DefaultTemperature > 0 {
+		v := r.DefaultTemperature
+		temperature = &v
+	}
+
+	req := llm.ChatRequest{
+		Model:       t.Agent.Model,
+		Messages:    messages,
+		Temperature: temperature,
+		MaxTokens:   t.Agent.MaxTokens,
+	}
+
+	start := time.Now()
+	resp, err := r.Client.ChatStream(ctx, req, func(delta string) {
+		if delta == "" {
+			return
+		}
+		writeAssistantTextLine(stdout, delta)
+	})
+	if err != nil {
+		writeResultLine(stdout, "error", err.Error(), 0, 0)
+		return fmt.Errorf("local runner: chat: %w", err)
+	}
+	elapsed := time.Since(start)
+
+	// Write one consolidated assistant envelope containing the full response.
+	// extractSummary and ParseChangestatFromOutput operate per-line, so a
+	// single envelope with the full text is what they expect to find.
+	if resp.Content != "" {
+		writeAssistantTextLine(stdout, resp.Content)
+	}
+	writeResultLine(stdout, "success", "", resp.PromptTokens, resp.OutputTokens)
+
+	e.CostUSD = 0
+	e.TokensIn = int64(resp.PromptTokens)
+	e.TokensOut = int64(resp.OutputTokens)
+
+	if r.Logger != nil {
+		r.Logger.Info("local runner completed",
+			"taskID", t.ID,
+			"model", resp.Model,
+			"tokens_in", resp.PromptTokens,
+			"tokens_out", resp.OutputTokens,
+			"finish_reason", resp.FinishReason,
+			"elapsed_ms", elapsed.Milliseconds(),
+		)
+	}
+	return nil
+}
+
+// writeAssistantTextLine writes a single stream-json line wrapping `text` as
+// an assistant text block. Format matches what ClaudeRunner emits, so
+// extractSummary and ParseChangestatFromFile read it transparently.
+func writeAssistantTextLine(w *os.File, text string) {
+	line := struct {
+		Type    string `json:"type"`
+		Message struct {
+			Content []struct {
+				Type string `json:"type"`
+				Text string `json:"text"`
+			} `json:"content"`
+		} `json:"message"`
+	}{Type: "assistant"}
+	line.Message.Content = []struct {
+		Type string `json:"type"`
+		Text string `json:"text"`
+	}{{Type: "text", Text: text}}
+	b, err := json.Marshal(line)
+	if err != nil {
+		return
+	}
+	w.Write(b)
+	w.Write([]byte("\n"))
+}
+
+// writeResultLine writes a final stream-json terminator line that downstream
+// parsers can recognise. Mirrors the shape of the result line ClaudeRunner emits.
+func writeResultLine(w *os.File, subtype, errMsg string, promptTokens, outputTokens int) {
+	line := map[string]any{
+		"type":            "result",
+		"subtype":         subtype,
+		"is_error":        errMsg != "",
+		"prompt_tokens":   promptTokens,
+		"output_tokens":   outputTokens,
+		"total_cost_usd":  0.0,
+	}
+	if errMsg != "" {
+		line["result"] = errMsg
+	}
+	b, err := json.Marshal(line)
+	if err != nil {
+		return
+	}
+	w.Write(b)
+	w.Write([]byte("\n"))
+}