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.

tsconfig.base.json

@@ -34,9 +34,6 @@
       "@cordisjs/plugin-timer": ["./vendor/timer/src"],
       "@cordisjs/plugin-hmr": ["./vendor/hmr/src"],
       "@cordisjs/plugin-logger-console": ["./vendor/logger-console/src"],
-      "@deepseek-ai/dsh-tool-fs/read": ["./packages/fs/tool-fs/src/read.ts"],
-      "@deepseek-ai/dsh-tool-fs/write": ["./packages/fs/tool-fs/src/write.ts"],
-      "@deepseek-ai/dsh-tool-fs/edit": ["./packages/fs/tool-fs/src/edit.ts"],
       // One wildcard maps every @deepseek-ai/dsh-<name> to its source. Package
       // dir names are unique across groups, so first-on-disk-wins resolution is
       // unambiguous; adding a package under an existing group needs no edit