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, 8 insertions, 0 deletions

diff --git a/src/features/workspaces/store.svelte.ts b/src/features/workspaces/store.svelte.ts
index 0f662dc..0cf4ce2 100644
--- a/src/features/workspaces/store.svelte.ts
+++ b/src/features/workspaces/store.svelte.ts
@@ -21,6 +21,8 @@ export interface WorkspaceStore {
 	rename(id: string, title: string): Promise<WorkspaceResult<Workspace>>;
 	/** Set/clear a workspace's default cwd. */
 	setDefaultCwd(id: string, defaultCwd: string | null): Promise<WorkspaceResult<Workspace>>;
+	/** Set/clear a workspace's default computer (SSH `Host` alias; null = local). */
+	setDefaultComputer(id: string, computerId: string | null): Promise<WorkspaceResult<Workspace>>;
 	/** Delete a workspace (closes its conversations, reassigns to "default"). */
 	remove(id: string): Promise<WorkspaceResult<{ closedCount: number }>>;
 }
@@ -71,6 +73,12 @@ export function createWorkspaceStore(http: WorkspaceHttp): WorkspaceStore {
 			return result;
 		},
 
+		async setDefaultComputer(id, computerId): Promise<WorkspaceResult<Workspace>> {
+			const result = await http.setDefaultComputer(id, computerId);
+			if (result.ok) void this.refresh();
+			return result;
+		},
+
 		async remove(id): Promise<WorkspaceResult<{ closedCount: number }>> {
 			const result = await http.delete(id);
 			if (result.ok) void this.refresh();