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, 31 insertions, 0 deletions

diff --git a/src/features/computer/index.ts b/src/features/computer/index.ts
new file mode 100644
index 0000000..656f6c2
--- /dev/null
+++ b/src/features/computer/index.ts
@@ -0,0 +1,31 @@
+export type {
+	Badge,
+	ComputerListResult,
+	ComputerSaveResult,
+	ComputerStatusResult,
+	ComputerStatusView,
+	ComputerView,
+	LoadComputerStatus,
+	LoadComputers,
+	SaveComputer,
+	TestComputer,
+	TestComputerResult,
+	TestResultView,
+} from "./logic/view-model";
+export {
+	formatHost,
+	knownHostLabel,
+	summarizeComputers,
+	viewComputer,
+	viewComputerStatus,
+	viewComputers,
+	viewTestResult,
+} from "./logic/view-model";
+export { default as ComputerField } from "./ui/ComputerField.svelte";
+export { default as ComputerSelect } from "./ui/ComputerSelect.svelte";
+
+/** Public module manifest — aggregated by the shell's "Loaded Modules" view. */
+export const manifest = {
+	name: "computer",
+	description: "Per-conversation / per-workspace SSH computer selection + status",
+} as const;