fix(passport-photo): require the face-detection bundle, not just background-removal (#329)

* fix(passport-photo): require the face-detection bundle, not just background-removal

Passport Photo runs face-landmark detection (face_landmarks.py, gated to the
face-detection bundle) before background removal (background-removal bundle),
but it was only declared under and guarded against background-removal. A user
who installed only Background Removal passed every JS-side check, then hit a
late "feature_not_installed" from the Python dispatcher gate when the analyze
step ran face landmarks, and the UI never told them Face Detection was needed.

- shared: add TOOL_EXTRA_BUNDLES + getRequiredBundlesForTool so a tool can
  declare more than one required bundle (passport-photo needs background-removal
  and face-detection). enablesTools is untouched, so the one-tool-per-bundle
  invariant still holds.
- api: isToolInstalled() now checks every required bundle; add
  getFirstMissingBundleForTool() so the analyze and base routes, pipeline (both
  guards) and batch report the bundle the user actually still needs.
- web: the proactive install prompt (tool-page) and features-store treat a tool
  as installed only when all required bundles are present, and point the prompt
  at the first missing one (sequential install, no new UI).

Refs #327

* test(passport-photo): deterministic integration coverage for the two-bundle guard

Boots the real API with an isolated DATA_DIR and controls installed.json to
prove the HTTP route behavior end-to-end:
- nothing installed -> 501 naming background-removal
- only background-removal installed -> 501 naming face-detection (issue #327)
- both installed -> guard passes (not 501)
- base route reports face-detection too

Refs #327

tests/unit/shared/features.test.ts

@@ -1,9 +1,11 @@
 import {
   FEATURE_BUNDLES,
   getBundleForTool,
+  getRequiredBundlesForTool,
   getToolsForBundle,
   PYTHON_SIDECAR_TOOLS,
   TOOL_BUNDLE_MAP,
+  TOOL_EXTRA_BUNDLES,
 } from "@snapotter/shared";
 import { describe, expect, it } from "vitest";
 
@@ -100,3 +102,51 @@ describe("Feature bundle edge cases", () => {
     }
   });
 });
+
+describe("getRequiredBundlesForTool", () => {
+  it("returns the primary bundle for a single-bundle tool", () => {
+    expect(getRequiredBundlesForTool("remove-background")).toEqual(["background-removal"]);
+  });
+
+  it("returns [] for non-AI tools", () => {
+    expect(getRequiredBundlesForTool("resize")).toEqual([]);
+    expect(getRequiredBundlesForTool("nonexistent-tool")).toEqual([]);
+  });
+
+  it("includes the primary bundle plus extras for cross-bundle tools", () => {
+    // Passport Photo runs face-landmark detection (face-detection) on top of
+    // background removal (its primary bundle).
+    expect(getRequiredBundlesForTool("passport-photo")).toEqual([
+      "background-removal",
+      "face-detection",
+    ]);
+  });
+
+  it("lists the primary bundle first", () => {
+    for (const toolId of PYTHON_SIDECAR_TOOLS) {
+      const required = getRequiredBundlesForTool(toolId);
+      if (required.length > 0) {
+        expect(required[0]).toBe(TOOL_BUNDLE_MAP[toolId]);
+      }
+    }
+  });
+
+  it("never lists a bundle twice", () => {
+    for (const toolId of PYTHON_SIDECAR_TOOLS) {
+      const required = getRequiredBundlesForTool(toolId);
+      expect(new Set(required).size).toBe(required.length);
+    }
+  });
+});
+
+describe("TOOL_EXTRA_BUNDLES", () => {
+  it("references only real bundles and never the tool's own primary bundle", () => {
+    for (const [toolId, extras] of Object.entries(TOOL_EXTRA_BUNDLES)) {
+      const primary = TOOL_BUNDLE_MAP[toolId];
+      for (const bundleId of extras) {
+        expect(FEATURE_BUNDLES[bundleId], `Unknown extra bundle ${bundleId}`).toBeDefined();
+        expect(bundleId, `${toolId} lists its primary bundle as an extra`).not.toBe(primary);
+      }
+    }
+  });
+});