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, 2 insertions, 0 deletions

diff --git a/GLOSSARY.md b/GLOSSARY.md
index fe4360c..7914ef5 100644
--- a/GLOSSARY.md
+++ b/GLOSSARY.md
@@ -24,6 +24,8 @@
 | **context window** | The model's MAXIMUM token capacity (the limit a **context size** is measured against). A FUTURE backend field — not on the wire yet. **Placeholder:** the composer status bar currently HARDCODES a `1,000,000`-token window for the `size / limit · pct%` readout + fill bar; swap to the real per-model value when the backend ships it (see `backend-handoff.md` §3). | max context, token limit (distinct from **context size**, the current usage) |
 | **message queue** | A per-conversation buffer of user messages awaiting mid-turn **steering** delivery (owned by the `message-queue` backend extension). Transient + in-memory; exposed to the FE as a per-conversation **surface** (`message-queue`, scope `conversation`; one `custom` field, `rendererId: "message-queue"`, `payload: QueuePayload`). NOT on the chat stream — it is control/state. Enqueued via `chat.queue` (WS) or `POST /conversations/:id/queue` (HTTP); auto-starts a turn if idle. `[email protected]`. | pending messages, steering queue |
 | **steering** | A user message injected into an in-flight turn at the tool-result boundary (drawn from the **message queue**): the model sees it alongside the tool results and may adjust course. Emitted on the chat stream as a `steering` `AgentEvent` (`TurnSteeringEvent`); the queue surface clears on drain (move, don't duplicate). If the turn ends with a non-empty queue (no tool call fired), the queue carries into a NEW turn as its opening prompt (no `steering` event). `[email protected]`. | mid-turn injection, course correction, interruption |
+| **computer** | A remote SSH target discovered from the system's `~/.ssh/config` — a read-only VIEW, NOT an editable entity (no CRUD store; to add one the user edits `~/.ssh/config`). Backend-canonical (`[email protected]`, additive). On the wire as `Computer` (`{ alias, hostName, port, user, identityFile, knownHost }`) + `ComputerEntry extends Computer` (adds `usageCount`, for `GET /computers`). `alias` IS the **computerId** — the string persisted per-conversation / per-workspace (the computer analog of `cwd`). Resolution is SERVER-owned (never re-implement): per-conversation `computerId` → `workspace.defaultComputerId` → `null`/local. USER-facing only: a tool-execution target forwarded to tools, NEVER part of the model prompt (does not affect prompt caching); the agent never sees it. HTTP API (`GET /computers`, `GET`/`PUT /conversations/:id/computer`, `PUT /workspaces/:id/default-computer`, `GET /computers/:alias/status`, `POST /computers/:alias/test`) consumed in handoff #2. | ssh host, remote host, server, connection target |
+| **computerId** | The string id of a **computer** — an SSH config `Host` alias users select. Persisted per-conversation and per-workspace (the computer analog of `cwd`/`workspaceId`). `null` means local (no SSH; today's behavior). On `Workspace` as the REQUIRED `defaultComputerId: string \| null` (null = local / no SSH; the computer analog of `defaultCwd`); per-conversation persistence via `GET`/`PUT`/`DELETE /conversations/:id/computer`. `chat.send` need not send it (resolved server-side from the persisted per-conversation value in the MVP). | ssh alias, host id, remote id |
 
 ## Frontend-specific
 | Term | Meaning | Aliases to avoid |