fix(tooling): set bun as javascript package manager so moon auto-installs deps

With 'javascript: {}', moon v2 never adds an InstallDependencies action
to the graph, so fresh clones fail with 'vite: command not found' when
running any web/api task (#846). The javascript toolchain drives
installs and must be told bun is the package manager.

Also drop 'bun.installDependencies: true' (defaults to true, and was
inert without packageManager set) and stale comments.

Fixes #846

Co-authored-by: Maze <mazeincoding@users.noreply.github.com>

.moon/toolchains.yml

@@ -1,12 +1,9 @@
 $schema: 'https://moonrepo.dev/schemas/toolchains.json'
 
-# javascript must be enabled alongside bun
-javascript: {}
+javascript:
+  packageManager: 'bun'
 
 bun:
   version: '1.3.11'
-  # Auto-install deps when lockfile/manifest changes
-  installDependencies: true
 
-# Version is inherited from .prototools (versionFromPrototools)
 rust: {}