refactor(tool-fs): drop per-tool subpath plugins; adopt single-tsconfig build

Adapt the four fs packages to master's single-tsconfig build convention
(lib/types outDir + types path + files allowlist), brought in by the merge.

While doing so, drop dsh-tool-fs's /read//write//edit subpath plugins. They
were the only subpath-export package in the tree and forced bespoke tsdown,
tsconfig path, package.json files, and workspace-constraint handling that no
sibling tool package (e.g. dsh-tool-bash) carries, for a focused-deployment
use case no consumer needed. dsh-tool-fs is now a single root plugin that
registers read/write/edit, mirroring dsh-tool-bash; the per-tool registration
helpers stay internal modules the root composes. The file-context event-gate
RFC is amended to record the narrowed scope.

packages/fs/fs-local/package.json

@@ -15,7 +15,9 @@
     "./package.json": "./package.json"
   },
   "files": [
-    "lib",
+    "lib/index.js",
+    "lib/types/**/*.d.ts",
+    "lib/types/**/*.d.ts.map",
     "src"
   ],
   "license": "BSD-3-Clause",