fix(app): use module-level slot for TitlebarRight to fix direct session URL crash

[TomKalina]

Summary

Direct navigation to /server/{key}/session/{id} routes crashes with:

Error: TitlebarRight must be used within TitlebarRightProvider

even though the provider is mounted. The error boundary catches it and shows "Something went wrong".

Root cause

SolidJS context propagation across lazy-loaded route chunks: the useContext lookup in TitlebarRight (session-header.tsx, in route chunk) fails to find the provider that lives in the main chunk (shell.tsx).

Verified via console logs in production build:

• [Provider] mounted fires successfully in the main chunk
• [Mount] has slot — TitlebarRightMount (in shell.tsx, same chunk as Provider) sees the context
• [useSlot] context lookup: MISSING — TitlebarRight (in lazy-loaded route-*.js chunk) cannot find the context

This is the same class of bug as #30898 ("ServerSync context must be used within a context provider"), which is still open.

In Vite dev mode (HMR) the bug does not reproduce — context propagation works correctly there.

Fix

Replace createContext/useContext with a module-level singleton slot. Both the provider and consumers reference the same module-level instance, sidesteping the cross-chunk context lookup entirely.

• TitlebarRightProvider becomes a no-op wrapper (kept for backward compatibility / minimal diff)
• createTitlebarRightSlot factory is preserved for the existing unit test
• All other call sites (TitlebarRightMount, TitlebarRight) reference the module-level slot directly

Verification

Built opencode2 v2 binary from this branch, deployed, and tested:

• ✅ Direct URL navigation to /server/{key}/session/{id} loads session content
• ✅ Click from home page session list works
• ✅ Back/forward browser navigation works
• ✅ Newly created sessions display correctly (v1/v2 storage mismatch also resolved via PR refactor(app): remove V1 client compatibility #43045 in v2 branch)

$ curl -u opencode:**** http://127.0.0.1:4096/api/session/ses_.../message?limit=20 | jq '.data | length'
3

Diff

Single file change (packages/app/src/shell/titlebar/right-slot.tsx):

-const TitlebarRightContext = createContext<TitlebarRightSlot>()
+// Module-level singleton slot. The provider and consumers all reference this
+// instance, which sidesteps SolidJS context propagation issues across lazy-loaded
+// route chunks where useSlot would otherwise throw "must be used within
+// TitlebarRightProvider" even though the provider is mounted.
+const [slotStore, setSlotStore] = createStore<{ mount?: HTMLElement; registrations: symbol[] }>({
+  registrations: [],
+})
+
+const slot: TitlebarRightSlot = { ... }
 
 export function TitlebarRightProvider(props: ParentProps) {
-  return (
-    <TitlebarRightContext.Provider value={createTitlebarRightSlot()}>{props.children}</TitlebarRightContext.Provider>
-  )
+  return <>{props.children}</>
 }

Related

• Refs OpenCode Web: direct session route crashes with "ServerSync context must be used within a context provider" on 1.16.0 #30898 — same class of bug ("ServerSync context must be used within a context provider" on direct session route)
• Depends on refactor(app): remove V1 client compatibility #43045 (remove V1 client compatibility) which is already merged into v2

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