feat(models): numbered OpenCode credential selection, labels, migration

Adopt the numbered OPENCODE_API_KEY_N scheme in the model picker and
concurrency surfaces.

- model-select: numeric sort of opencode-<n> keys (#2 before #10); friendly
  OpenCode #N labels (raw opencode-N/<model> value still selected/persisted);
  migrateLegacyModelName rewrites opencode/<model> -> opencode-1/<model>.
- ModelSelector: renders friendly key labels; surfaces a disappeared saved
  credential as UNAVAILABLE (disabled option + notice) without silently
  switching to another model.
- app store: DEFAULT_MODEL -> opencode-1/...; catalogs no longer auto-fallback
  the active model when the selected credential is absent; boot restore
  migrates persisted legacy opencode/<model> tab models idempotently.
- concurrency: providerLabel renders opencode-<n> as OpenCode #<n> in the
  limit rows and Add dropdown (raw provider id preserved on the wire).
- Tests: parsing/sorting/labels/migration, unavailable-state selector behavior,
  no-silent-fallback, and concurrency provider label; fixtures updated to the
  numbered scheme.

Verification: bun install, bun run typecheck (0 errors), bun run test
(1179 passed), bun run check (clean, exit 0), bun run build (vite OK).

3 files changed, 7 insertions, 5 deletions

diff --git a/src/features/concurrency/ui/ConcurrencyLimitRow.svelte b/src/features/concurrency/ui/ConcurrencyLimitRow.svelte
index bf06ac0..c8f6c8f 100644
--- a/src/features/concurrency/ui/ConcurrencyLimitRow.svelte
+++ b/src/features/concurrency/ui/ConcurrencyLimitRow.svelte
@@ -4,6 +4,7 @@
     DEFAULT_COOLDOWN_MS,
     parseCooldownInput,
     parseLimitInput,
+    providerLabel,
     statusLabel,
     type Badge,
     type ConcurrencyLimitView,
@@ -132,8 +133,8 @@
        the buttons never wrap; tight gap + narrow inputs keep the provider name
        visible; the provider shrinks via flex-1 + min-w-0). -->
   <div class="flex flex-nowrap items-center gap-1">
-    <span class="min-w-0 flex-1 truncate font-medium font-mono" title={limit.providerId}
-      >{limit.providerId}</span
+    <span class="min-w-0 flex-1 truncate font-medium" title={limit.providerId}
+      >{providerLabel(limit.providerId)}</span
     >
     <input
       type="text"
diff --git a/src/features/concurrency/ui/ConcurrencyView.svelte b/src/features/concurrency/ui/ConcurrencyView.svelte
index aadb8d1..2e23f5c 100644
--- a/src/features/concurrency/ui/ConcurrencyView.svelte
+++ b/src/features/concurrency/ui/ConcurrencyView.svelte
@@ -6,6 +6,7 @@
     DEFAULT_COOLDOWN_MS,
     parseCooldownInput,
     parseLimitInput,
+    providerLabel,
     providerOptions,
     summarizeLimits,
     viewConcurrencyLimits,
@@ -376,7 +377,7 @@
               <option value="" disabled>No providers available</option>
             {:else}
               {#each providerOpts as provider (provider)}
-                <option value={provider}>{provider}</option>
+                <option value={provider}>{providerLabel(provider)}</option>
               {/each}
             {/if}
           </select>
diff --git a/src/features/concurrency/ui/ConcurrencyView.test.ts b/src/features/concurrency/ui/ConcurrencyView.test.ts
index a8163c2..e214692 100644
--- a/src/features/concurrency/ui/ConcurrencyView.test.ts
+++ b/src/features/concurrency/ui/ConcurrencyView.test.ts
@@ -11,8 +11,8 @@ import type {
 } from "../logic/types";
 import ConcurrencyView from "./ConcurrencyView.svelte";
 
-// Available models → provider ids are "umans", "anthropic", "openai-compat".
-const MODELS = ["umans/umans-glm-5.2", "anthropic/claude-sonnet", "openai-compat/gpt-4o"] as const;
+// Available models → provider ids are "umans", "anthropic", "opencode-1".
+const MODELS = ["umans/umans-glm-5.2", "anthropic/claude-sonnet", "opencode-1/gpt-4o"] as const;
 
 // A status entry factory (defaults to a healthy limited provider). The new
 // concurrency-fixes fields (`cooldownMs`, `autoReduced`) are always present.