T01.i: delete the dead bun store, stop it from coming back

node_modules/.bun held stale @ng-org/web, @ng-org/shex-orm and
@ng-org/alien-deepsignals copies beside the pnpm-managed current ones
(T01.h left it in place, latent). Deleted the directory; every symlink
in the tree already resolved through node_modules/.pnpm, so nothing
pointed at it.

The likely trigger for a future accidental bun install was a bun.lock
committed at the repo root (the gitignore only listed the older
bun.lockb, so this text-format lockfile slipped through). Removed the
tracked bun.lock and added both bun.lock and bun.lockb to .gitignore,
and declared packageManager: pnpm@10.26.0 in package.json so tooling
(and anyone reading it) has one unambiguous answer for which installer
this tree uses. No new tooling built, per the task's instruction.

package.json

@@ -2,6 +2,7 @@
   "name": "ng-eventually",
   "private": true,
   "type": "module",
+  "packageManager": "pnpm@10.26.0",
   "description": "Generic polyfill layer over the NextGraph JS SDK — makes a single broker behave like the (not-yet-shipped) multi-user NextGraph: emulated capabilities and inbox. Drop-in SDK-shaped client; remove at migration. (A global-index curator package is deferred — see README.)",
   "workspaces": [
     "packages/*",