fix(review): bound E2B readBytes at the seam, prove conditional-registration disposal, and align read_image contracts

- E2BFileSystem.readBytes now short-circuits on the stat size before any
  content transfer and streams the remote object, cancelling at the first
  chunk past the cap, honoring the seam's bounded-buffering contract; the
  fs-e2b README pair documents the new primitive.
- The tool-fs HMR test now proves the attachments-scoped registration:
  disposing the store withdraws read_image while read/write/edit stay,
  remounting restores it, and disposing the plugin withdraws everything.
- read_image caps reads at the smaller of maxImageBytes and
  maxMessageImageBytes, records an absent observation for a missing
  target like its sibling read, widens the mismatch remedy to cover
  out-of-family formats, and renames the gate's parameter to
  requestedPath; module/apply/registration JSDoc now match the shipped
  composition. zh terminology aligned; the examples manifest keeps its
  literal arrow.

packages/fs/tool-fs/src/index.ts

@@ -1,5 +1,5 @@
 /**
- * Model-facing read, write, and edit tools over `ctx.fs`. This package owns schemas, validation,
+ * Model-facing read, read_image, write, and edit tools over `ctx.fs`. This package owns schemas, validation,
  * read windows, formatting, and observation events, never a concrete provider. An optional
  * event policy supplies mutation guards; without one the tools use unconditional provider calls.
  * @module @deepseek-ai/dsh-tool-fs
@@ -50,7 +50,7 @@ function assertPositiveInteger(name: string, value: number): void {
   }
 }
 
-/** Register the full `read`/`write`/`edit` filesystem tool suite. */
+/** Register the full `read`/`write`/`edit` filesystem tool suite, plus `read_image` while `attachments` is mounted. */
 export function apply(ctx: Context, config: Config): void {
   // schemastery (Config) has already filled every defaulted field.
   const resolved = config as ResolvedConfig