feat(api): enrich CI failure task instructions via local LLM

Phase 3 of "local OSS models as agents" plan. When the webhook handler
creates a task for a failed CI run AND a local LLM is configured on
the server, the hardcoded 4-step investigation template is replaced
with a project-aware investigation plan generated by the LLM.

Scope adjustment from the original sketch: the original plan said
"summarize fetched workflow logs", but fetching logs requires GitHub
API auth that isn't wired. Narrowed to project-context triage —
recent git log + CLAUDE.md content + webhook metadata, fed to the
LLM with a system prompt asking for 6-12 lines of concrete next
steps. Deferred GitHub log fetching to post-epic cleanup.

Implementation:
- New internal/api/webhook_llm.go holds enrichCIInstructions and its
  helpers (readRecentCommits via `git log`, readProjectDoc).
- enrichCIInstructions is truly additive: any failure mode (no client,
  HTTP error, empty body, 10s timeout) returns the original fallback
  template unchanged. Existing webhook tests pass byte-for-byte.
- Always preserves a metadata header (repo/branch/SHA/check/URL)
  ahead of the LLM body so investigators don't lose context if the
  LLM is terse.
- Reuses s.llm (set via Server.SetLLM in Phase 2) — no new config
  knob, no per-feature gating. Asymmetric opt-out (yes-elaborate,
  no-CI-triage) deferred until there's actual demand.

Tests:
- enrichCIInstructions: nil client, LLM 500, empty body all return
  fallback unchanged.
- enrichCIInstructions: success path produces enriched body with
  metadata header preserved; user prompt contains repo/branch/SHA.
- enrichCIInstructions: real git repo (init + 2 commits) → recent
  commits appear in user prompt.
- Webhook handler regression guard: no-LLM path produces the exact
  legacy template substrings.
- Webhook handler with LLM stubbed: task instructions contain LLM
  body + metadata header.

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

https://claude.ai/code/session_017Edeq947TpSm1vQTxMhi1J

1 files changed, 14 insertions, 1 deletions

diff --git a/internal/api/webhook.go b/internal/api/webhook.go
index 8bf1676..9437f7d 100644
--- a/internal/api/webhook.go
+++ b/internal/api/webhook.go
@@ -1,6 +1,7 @@
 package api
 
 import (
+	"context"
 	"crypto/hmac"
 	"crypto/sha256"
 	"encoding/hex"
@@ -154,7 +155,7 @@ func (s *Server) handleWorkflowRunEvent(w http.ResponseWriter, body []byte) {
 func (s *Server) createCIFailureTask(w http.ResponseWriter, repoName, fullName, branch, sha, checkName, htmlURL string) {
 	project := matchProject(s.projects, repoName)
 
-	instructions := fmt.Sprintf(
+	fallback := fmt.Sprintf(
 		"A CI failure has been detected and requires investigation.\n\n"+
 			"Repository: %s\n"+
 			"Branch: %s\n"+
@@ -169,6 +170,18 @@ func (s *Server) createCIFailureTask(w http.ResponseWriter, repoName, fullName,
 		fullName, branch, sha, checkName, htmlURL,
 	)
 
+	tctx := ciTriageContext{
+		Repo:      fullName,
+		Branch:    branch,
+		SHA:       sha,
+		CheckName: checkName,
+		URL:       htmlURL,
+	}
+	if project != nil {
+		tctx.ProjectDir = project.Dir
+	}
+	instructions := enrichCIInstructions(context.Background(), s.llm, tctx, fallback)
+
 	now := time.Now().UTC()
 	t := &task.Task{
 		ID:   uuid.New().String(),