fix(ralph-loop): generate transcript path from sessionID instead of relying on event properties (#355)

OpenCode doesn't pass transcriptPath in the session.idle event properties,
which caused detectCompletionPromise to always return false (the first check
returns early if transcriptPath is undefined).

This fix:
- Imports getTranscriptPath from claude-code-hooks/transcript
- Generates the transcript path from sessionID instead of reading from event
- Adds optional getTranscriptPath callback to RalphLoopOptions for testability

Fixes #354

Co-authored-by: sisyphus-dev-ai <sisyphus-dev-ai@users.noreply.github.com>

src/hooks/ralph-loop/index.test.ts

@@ -329,17 +329,19 @@ describe("ralph-loop", () => {
 
     test("should detect completion promise and stop loop", async () => {
       // #given - active loop with transcript containing completion
-      const hook = createRalphLoopHook(createMockPluginInput())
+      const transcriptPath = join(TEST_DIR, "transcript.jsonl")
+      const hook = createRalphLoopHook(createMockPluginInput(), {
+        getTranscriptPath: () => transcriptPath,
+      })
       hook.startLoop("session-123", "Build something", { completionPromise: "COMPLETE" })
 
-      const transcriptPath = join(TEST_DIR, "transcript.jsonl")
       writeFileSync(transcriptPath, JSON.stringify({ content: "Task done <promise>COMPLETE</promise>" }))
 
-      // #when - session goes idle with transcript
+      // #when - session goes idle (transcriptPath now derived from sessionID via getTranscriptPath)
       await hook.event({
         event: {
           type: "session.idle",
-          properties: { sessionID: "session-123", transcriptPath },
+          properties: { sessionID: "session-123" },
         },
       })