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.

.gitignore

@@ -2,6 +2,7 @@ node_modules/
 dist/
 *.tsbuildinfo
 .DS_Store
+bun.lock
 bun.lockb
 
 # SDK e2e real-broker harness — dedicated wallet profile + bundle (never committed)