docs: reserve seam for complete capabilities

packages/fs/fs-local/src/fsio.ts

@@ -70,7 +70,7 @@ function versionOf(info: BigIntStats): FsVersion {
 }
 
 /**
- * Test seam: lets specs pin the atomic-write temp names (to prove
+ * Test hook: lets specs pin the atomic-write temp names (to prove
  * exclusive-open behavior without a name race) and observe the staged temp
  * file before it is renamed over the target.
  */
@@ -427,7 +427,7 @@ async function removeStagingDirOrThrow(stagingDir: string, originalError: unknow
  * @param mode - existing destination's POSIX mode to preserve, or `undefined` for a new file;
  * inert as a mode on Windows but identifies replacement security semantics.
  * @param signal - cancellation checked before the final rename.
- * @param internals - test seam for pinning temp names and observing the staged file.
+ * @param internals - Test hook for pinning temp names and observing the staged file.
  */
 export async function writeFileAtomic(
   absolutePath: string,

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

@@ -56,7 +56,7 @@ export class LocalFileSystem extends FileSystem {
 
   /** Validated config (schemastery applied the defaults before construction). */
   readonly config: ResolvedConfig
-  /** Test seam forwarded to fsio (force streaming path, pin temp names). */
+  /** Test hook forwarded to fsio (force streaming path, pin temp names). */
   internals: FsIoInternals = {}
   /** Per-targetKey tail promise: serializes mutating ops so the read→guard→write
    * window can't interleave, making concurrent writes/edits deterministically