refactor: remove duplicate memory-store, use existing SF memory infrastructure

- Removed redundant src/db/memory-store.ts (was duplicate of existing memory system)
- Removed duplicate memory extension folder
- SF already has complete memory infrastructure:
  * memory-store.js (core CRUD + ranking)
  * memory-embeddings.js (vector ops, Float32Array BLOB storage)
  * memory-embeddings-llm-gateway.js (semantic ranking)
  * memory-relations.js (relationship graph)
  * memory-ingest.js (ingestion from files/URLs)
  * memory-extractor.js (auto-learning from units)
  * memory-sleeper.js (decay/supersession)
  * commands-memory.js (CLI interface)
- Uses Node 24 SQLite via sf-db.js (not separate package)
- VectorDrive kept as fallback extension
- Next: Integrate UOK kernel with existing memory system

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/resources/extensions/sf/autonomous-solver.js

@@ -635,7 +635,17 @@ export function buildAutonomousSolverMissingCheckpointRepairPrompt(
 			`- ${diagnosis.classification}: ${diagnosis.summary ?? "missing checkpoint"}`,
 		);
 	}
-	if (repairAttempt <= 1) {
+	if (diagnosis?.classification === "no-transcript") {
+		lines.push(
+			"",
+			"No transcript was captured from your previous turn. To reconstruct the checkpoint:",
+			"1. Read .sf/runtime/autonomous-solver/LOOP.md to see what was expected.",
+			"2. List files in the milestone/slice/task directories to find what artifacts exist.",
+			"3. Read any SUMMARY.md or PLAN.md files to understand what progress was made.",
+			"4. Based on the evidence, call sf_autonomous_checkpoint with the appropriate outcome and PDD fields.",
+			"5. If you cannot determine what happened, use outcome='decide' and ask the human what the checkpoint should contain.",
+		);
+	} else if (repairAttempt <= 1) {
 		lines.push("Do not continue implementation work in this repair turn.");
 	} else {
 		lines.push(

src/resources/extensions/sf/tests/autonomous-solver.test.mjs

@@ -281,6 +281,26 @@ describe("autonomous solver", () => {
 		expect(second).toHaveLength(0);
 	});
 
+	test("buildAutonomousSolverMissingCheckpointRepairPrompt_no_transcript_includes_filesystem_guidance", () => {
+		const prompt = buildAutonomousSolverMissingCheckpointRepairPrompt(
+			{ iteration: 2 },
+			"research-slice",
+			"M012/parallel-research",
+			{
+				classification: "no-transcript",
+				summary: "No agent-end transcript was available to classify.",
+			},
+			2,
+			4,
+		);
+
+		expect(prompt).toContain("no-transcript");
+		expect(prompt).toContain("No transcript was captured");
+		expect(prompt).toContain(".sf/runtime/autonomous-solver/LOOP.md");
+		expect(prompt).toContain("SUMMARY.md");
+		expect(prompt).toContain("outcome='decide'");
+	});
+
 	test("getConfiguredAutonomousSolverMaxIterations_clamps_preference", () => {
 		expect(getConfiguredAutonomousSolverMaxIterations()).toBe(30000);
 		expect(