fix(search): cross-platform dynamic import + Windows VC++ Redist hint

Two fixes for `axme-code config set context.mode search` on Windows:

1. **pathToFileURL on dynamic import.** `await import(absolutePath)`
   throws on Windows because Node treats raw `C:\...` paths as bare
   specifiers. Wrapping the resolved path with `pathToFileURL(...).href`
   produces a `file:///C:/...` URL that imports cleanly on every
   platform.

2. **Actionable error when onnxruntime-node native binding fails to
   load.** Most common Windows failure: `onnxruntime_binding.node`
   throws "specified module could not be found" because Microsoft
   Visual C++ Redistributable is missing. We now detect that
   signature and print a clear hint pointing to the redist installer
   plus the retry command, instead of returning null silently and
   leaving the user to chase a generic "module not loaded" message
   from search-install.ts.

Verified on Azure Win11 native:
- Before VC++ Redist install: error message correctly directs the
  user to https://aka.ms/vs/17/release/vc_redist.x64.exe.
- After VC++ Redist install: `axme-code config set context.mode
  search` succeeds end-to-end (31/31 entries indexed in 5s,
  embeddings.json written, config.yaml updated).
- claude --print session calls axme_context (renders search-mode
  catalog) and axme_search_kb (top hits semantically correct: D-004
  + D-002 for "git push force safety" query).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: George-iam

src/storage/embeddings.ts

@@ -26,6 +26,7 @@ import { createRequire } from "node:module";
 import { existsSync, statSync } from "node:fs";
 import { homedir } from "node:os";
 import { join } from "node:path";
+import { pathToFileURL } from "node:url";
 import { atomicWrite, ensureDir, readSafe } from "./engine.js";
 
 export type EmbedType = "memory" | "decision";
@@ -89,15 +90,36 @@ export async function loadEmbedder(): Promise<Embedder | null> {
   if (!isRuntimeInstalled()) return null;
 
   // Dynamic import via createRequire so we can resolve from the lazy runtime
-  // location at runtime regardless of where the CLI bundle lives. Typed as
-  // `any` because @huggingface/transformers is intentionally NOT a build-time
+  // location regardless of where the CLI bundle lives. Typed as `any`
+  // because @huggingface/transformers is intentionally NOT a build-time
   // dependency — it's lazy-installed on opt-in.
+  //
+  // pathToFileURL is mandatory on Windows: Node's dynamic import refuses
+  // raw absolute paths like `C:\...\index.js` (treats them as bare
+  // specifiers and looks for a package). file:// URLs work everywhere.
   const runtimeRequire = createRequire(join(RUNTIME_DIR, "node_modules", ".package-lock.json"));
   let mod: any;
   try {
     const requirePath = runtimeRequire.resolve("@huggingface/transformers");
-    mod = await import(requirePath);
-  } catch {
+    mod = await import(pathToFileURL(requirePath).href);
+  } catch (e) {
+    // The most common Windows failure mode here is "specified module could
+    // not be found" thrown while loading onnxruntime-node's native
+    // .node binding because Microsoft Visual C++ Redistributable isn't
+    // installed. Surface an actionable hint instead of returning null
+    // silently and leaving the user to interpret the deferred error.
+    const msg = (e as Error)?.message ?? String(e);
+    if (process.platform === "win32" && /could not be found|onnxruntime_binding\.node/i.test(msg)) {
+      process.stderr.write(
+        "AXME: failed to load semantic-search runtime. The most common cause on Windows is\n" +
+        "      a missing Microsoft Visual C++ Redistributable (required by onnxruntime-node).\n" +
+        "      Install from https://aka.ms/vs/17/release/vc_redist.x64.exe and retry\n" +
+        "      `axme-code config set context.mode search` (or `axme-code reindex`).\n" +
+        `      Underlying error: ${msg}\n`,
+      );
+    } else {
+      process.stderr.write(`AXME: failed to load semantic-search runtime: ${msg}\n`);
+    }
     return null;
   }