feat(computer): SSH computer selection + status + workspace default (handoff #2)

Mirrors the cwd/workspace UI for the SSH-computer feature:

- New feature library src/features/computer/:
  - logic/view-model.ts (pure): viewComputer/viewComputerStatus/viewTestResult/
    summarizeComputers/formatHost/knownHostLabel + state->badge for the 4
    ComputerStatusResponse states + SaveComputer/LoadComputerStatus/
    TestComputer/LoadComputers ports. 20 view-model tests.
  - ui/ComputerField.svelte: per-conversation selector (dropdown +
    connection-status badge + Test-connection, polling the selected alias).
  - ui/ComputerSelect.svelte: reusable Local/computers dropdown, shared with
    the workspace default-computer control.
- AppStore: computerId state + refreshComputer (at every focus site, parallel
  to refreshCwd) + setComputer (PUT /conversations/:id/computer, null=clear) +
  global computers catalog (GET /computers on boot, like models) +
  computerStatus(alias) + testComputer(alias). chat.send UNCHANGED (resolved
  server-side like cwd).
- App.svelte: ComputerField in the Model sidebar view next to CwdField; adapted
  ports wrap the store.
- workspaces: setDefaultComputer on WorkspaceHttp+WorkspaceStore
  (PUT /workspaces/:id/default-computer); default-computer selector in
  WorkspaceCard (reuses ComputerSelect); router passes store.computers through.
- Re-mirrored .dispatch/transport-contract.reference.md (Computers section +
  ChatRequest.computerId); updated .dispatch/wire.reference.md (Computer/
  ComputerEntry/defaultComputerId + the provider-retry divergence note from
  handoff #1); GLOSSARY + backend-handoff.md (handoff #2, §2e).

Transparency invariant: the computer is USER-facing only (a tool-execution
target, never part of the model prompt); the agent never sees it.

Verify: 795/795 tests green; biome clean; vite build succeeds; 0 typecheck
errors from the computer feature. (11 pre-existing svelte-check errors remain
from the open §2d provider-retry divergence — backend feature/ssh-support
still lacks TurnProviderRetryEvent; not from this feature.)

1 files changed, 23 insertions, 0 deletions

diff --git a/src/features/workspaces/adapter/http.ts b/src/features/workspaces/adapter/http.ts
index 97fc2e2..6ebfee1 100644
--- a/src/features/workspaces/adapter/http.ts
+++ b/src/features/workspaces/adapter/http.ts
@@ -1,6 +1,7 @@
 import type {
 	DeleteWorkspaceResponse,
 	EnsureWorkspaceRequest,
+	SetWorkspaceDefaultComputerRequest,
 	SetWorkspaceDefaultCwdRequest,
 	SetWorkspaceTitleRequest,
 	Workspace,
@@ -23,6 +24,7 @@ import type {
  * - `GET /workspaces/:id` (404 → null) → get
  * - `PUT /workspaces/:id/title` → rename
  * - `PUT /workspaces/:id/default-cwd` → set/clear default cwd
+ * - `PUT /workspaces/:id/default-computer` → set/clear default computer (SSH handoff #2)
  * - `DELETE /workspaces/:id` (409 for "default") → delete
  */
 export type WorkspaceResult<T> =
@@ -35,6 +37,7 @@ export interface WorkspaceHttp {
 	get(id: string): Promise<Workspace | null>;
 	setTitle(id: string, title: string): Promise<WorkspaceResult<Workspace>>;
 	setDefaultCwd(id: string, defaultCwd: string | null): Promise<WorkspaceResult<Workspace>>;
+	setDefaultComputer(id: string, computerId: string | null): Promise<WorkspaceResult<Workspace>>;
 	delete(id: string): Promise<WorkspaceResult<{ closedCount: number }>>;
 }
 
@@ -118,6 +121,26 @@ export function createWorkspaceHttp(httpBase: string, fetchImpl: typeof fetch):
 			}
 		},
 
+		async setDefaultComputer(id, computerId): Promise<WorkspaceResult<Workspace>> {
+			try {
+				const res = await fetchImpl(
+					`${httpBase}/workspaces/${encodeURIComponent(id)}/default-computer`,
+					{
+						method: "PUT",
+						headers: { "Content-Type": "application/json" },
+						body: JSON.stringify({ computerId } satisfies SetWorkspaceDefaultComputerRequest),
+					},
+				);
+				if (!res.ok) return { ok: false, error: await errText(res) };
+				return { ok: true, value: (await res.json()) as WorkspaceResponse };
+			} catch (err) {
+				return {
+					ok: false,
+					error: err instanceof Error ? err.message : "Set default computer failed",
+				};
+			}
+		},
+
 		async delete(id): Promise<WorkspaceResult<{ closedCount: number }>> {
 			try {
 				const res = await fetchImpl(`${httpBase}/workspaces/${encodeURIComponent(id)}`, {