feat(plugin-market-generator): add a reference index generator

Generate a validated format-1 plugin market index from a list of npm package
names and https Git repository URLs, without running package code.

- List every non-deprecated npm bundle version, and Git versions at release
  tags and the default branch, each with its engines.dsh range.
- Read display fields, keywords, homepage, and icons the way DSH reads
  installed plugins; inline small icons up to the format's 32 KiB limit.
- Cache results per immutable input and rewrite output only when it changes.

tsconfig.host.json

@@ -200,6 +200,7 @@
     "apps/web/tests/workflow-run.e2e.ts",
     "apps/web/stress-tests/reasoning-chunks.stress.ts",
     "apps/cli/tests/**/*.ts",
+    "apps/plugin-market-generator/tests/**/*.ts",
     "apps/desktop/scripts/**/*.ts",
     "apps/desktop/tests/**/*.ts",
     "apps/desktop-host/tests/**/*.ts",
@@ -526,6 +527,7 @@
     { "path": "./packages/lsp/lsp-stdio" },
     { "path": "./packages/lsp/tool-lsp" },
     { "path": "./apps/cli" },
+    { "path": "./apps/plugin-market-generator" },
     { "path": "./apps/desktop-host" },
     { "path": "./apps/desktop/tsconfig.host.json" }
   ]