fix(host): bound listDirectory levels at a configurable maxEntries

One list call now materializes at most maxEntries child rows (config,
default 1000 - GitHub's web-UI directory-listing bound). Candidates sort
before probing so a cut level keeps the name-sorted head and symlink
probing stops with the bound, and DirectoryListing carries a required
truncated flag on the seam and the wire so clients can state
incompleteness instead of silently missing tail entries.

packages/host/apiproxy/src/api/host.schema.ts

@@ -47,6 +47,7 @@ export const hostListDirectoryValueSchema = z.object({
   home: z.string(),
   crumbs: z.array(directoryEntrySchema),
   entries: z.array(directoryEntrySchema),
+  truncated: z.boolean(),
 }) satisfies z.ZodType<Wire<ResponseValue<'host.listDirectory'>>>
 
 /** host.createDirectory request payload: name must be one plain path segment. */

packages/host/apiproxy/src/api/host.ts

@@ -28,6 +28,8 @@ export interface DirectoryListing {
   crumbs: DirectoryEntry[]
   /** Direct child directories, name-sorted; symlinks to directories included. */
   entries: DirectoryEntry[]
+  /** True when the backend cut `entries` at its complete-result bound (the name-sorted tail is absent). */
+  truncated: boolean
 }
 
 /** Host-level unary methods. */

packages/host/apiproxy/tests/api-proxy-workspace.spec.ts

@@ -159,6 +159,7 @@ const BROWSE_STUB: DirectoryPickerCapability = {
       home: '/home/user',
       crumbs: [{ name: '/', path: '/', hidden: false }],
       entries: [{ name: 'projects', path: `${target}/projects`, hidden: false }],
+      truncated: false,
     }
   },
   createDirectory: async (path, name) => {

packages/host/apiproxy/tests/client-handler.spec.ts

@@ -50,7 +50,7 @@ function scriptedApi(overrides: {
     host: {
       describe: r => ok(r, { version: '0-test', cwd: '/t', attachedSessions: 0 }),
       pickDirectory: r => ok(r, { path: null }),
-      listDirectory: r => ok(r, { path: '/t', home: '/t', crumbs: [], entries: [] }),
+      listDirectory: r => ok(r, { path: '/t', home: '/t', crumbs: [], entries: [], truncated: false }),
       createDirectory: r => ok(r, { path: '/t/new' }),
       openPath: r => ok(r, { opened: true as const }),
       ...overrides.host,

packages/host/apiproxy/tests/fetch-carrier.spec.ts

@@ -82,7 +82,7 @@ function fakeApi(overrides: Partial<{ muxFrames: MuxFrame[]; hostFrames: HostFra
         return { rpcId: request.rpcId, result: { ok: true, value: { path: null } } }
       },
       async listDirectory(request) {
-        return { rpcId: request.rpcId, result: { ok: true, value: { path: '/w', home: '/w', crumbs: [{ name: '/', path: '/', hidden: false }], entries: [] } } }
+        return { rpcId: request.rpcId, result: { ok: true, value: { path: '/w', home: '/w', crumbs: [{ name: '/', path: '/', hidden: false }], entries: [], truncated: false } } }
       },
       async createDirectory(request) {
         return { rpcId: request.rpcId, result: { ok: true, value: { path: '/w/new' } } }
@@ -224,7 +224,7 @@ describe('unary round trip (handler ⇄ client, no network)', () => {
     const listed = await c.host.listDirectory({ path: '/w' })
     expect(listed.result).toEqual({
       ok: true,
-      value: { path: '/w', home: '/w', crumbs: [{ name: '/', path: '/', hidden: false }], entries: [] },
+      value: { path: '/w', home: '/w', crumbs: [{ name: '/', path: '/', hidden: false }], entries: [], truncated: false },
     })
     const home = await c.host.listDirectory({})
     expect(home.result).toMatchObject({ ok: true, value: { home: '/w' } })

packages/host/apiproxy/tests/rpc-schemas.spec.ts

@@ -231,8 +231,11 @@ describe('host domain schemas', () => {
       home: '/home/u',
       crumbs: [{ name: '/', path: '/', hidden: false }, { name: 'p', path: '/home/u/p', hidden: false }],
       entries: [{ name: '.dot', path: '/home/u/p/.dot', hidden: true }],
+      truncated: false,
     })
     expect(listing.entries[0]?.hidden).toBe(true)
+    // The flag is part of the wire value, not an optional decoration.
+    expect(() => hostListDirectoryValueSchema.parse({ path: '/x', home: '/x', crumbs: [], entries: [] })).toThrow()
     expect(hostCreateDirectoryRequestSchema.parse({ path: '/x', name: 'new' })).toEqual({ path: '/x', name: 'new' })
     for (const name of ['', ' ', '.', '..', 'a/b', 'a\\b']) {
       expect(() => hostCreateDirectoryRequestSchema.parse({ path: '/x', name })).toThrow()