fix(httpapi): install Instance ALS for adapter Promise bridge

[kitlangton]

Summary

The TUI's "New Workspace → Worktree" creates a workspace via POST /experimental/workspace. On the new Effect HttpApi backend the request returned a 500 with the toast `Failed to create workspace: unknown error`. Schema validation passed (PR #25412), but the inner handler tripped on `InstanceState.context` failing with `No context found for instance`.

This PR fixes the underlying bridge-context issue and adds a regression test that reproduces the live failure path against the real built-in `WorktreeAdapter`.

Reproduction

```
POST /experimental/workspace
backend = effect-httpapi
http.response.status_code = 500
exception.type = instance
exception.message = No context found for instance
at use (src/util/local-context.ts:15)
at instance-state.ts:29
at Workspace.create (control-plane/workspace.ts:463)
```

Root Cause

The HttpApi instance-context middleware sets `InstanceRef` on the request fiber via `InstanceStore.provide`. That works for any code that stays inside Effect.

`Workspace.create` calls into the `WorkspaceAdapter` via `Effect.promise(() => adapter.configure(...))`. `WorktreeAdapter.configure` is async JS that does `await loadWorktree()` then `await AppRuntime.runPromise(Worktree.makeWorktreeInfo())`. By the time the nested `AppRuntime.runPromise` reaches `attach()`, the parent Effect fiber is suspended in JS-promise-land:

• `Fiber.getCurrent()` returns `undefined` (no synchronous Effect fiber)
• `Instance.current` (legacy ALS) was never installed for HttpApi requests
• `InstanceRef` is unreachable across the async boundary

So `attach()` finds no instance context, the new fiber starts with `InstanceRef = undefined`, and `InstanceState.context` (which falls back to `Instance.current`) throws.

Node's `AsyncLocalStorage` does propagate across `async`/`await`. The fix is to install legacy `Instance.context`/`WorkspaceContext` ALS exactly at the Effect→JS bridge so any nested runtime call inherits it.

Fix

• Add `EffectBridge.adapterPromise(fn)` and `EffectBridge.adapterTryPromise(fn)` in `packages/opencode/src/effect/bridge.ts`. Each reads the current `InstanceRef` and `WorkspaceRef`, then runs the JS callback inside the existing `restore(instance, workspace, fn)` so both `Instance.context` and `WorkspaceContext` ALS are set for the duration of the callback.
• Replace every adapter Promise call site in `control-plane/workspace.ts` (`adapter.target`, `adapter.configure`, `adapter.create`, `adapter.remove`) with `EffectBridge.adapterPromise` / `adapterTryPromise`.
• Replace the same inline pattern in `server/routes/instance/httpapi/middleware/workspace-routing.ts` `resolveTarget`.

This keeps all bridging in one helper alongside the existing `EffectBridge.make` plumbing and avoids the `WorkspaceRef` ALS gap that would have appeared if I had open-coded the helper twice.

Tests

• New `packages/opencode/test/server/httpapi-workspace.test.ts > creates a real git worktree workspace via the builtin adapter` — drives the live failure path through the built-in `WorktreeAdapter`. Without this fix it returns 500 `No context found for instance`. With the fix it returns 200.
• `bun typecheck` passes
• `bun run test test/server/httpapi-workspace.test.ts test/control-plane/workspace.test.ts test/project/instance.test.ts test/effect/run-service.test.ts` — 57/57 pass
• Full `bun test` — only the two pre-existing baseline failures (`project.initGit endpoint`, `session.created event`) remain

Why this approach (and not the alternatives)

• I first tried wiring ALS install into `InstanceStore.provide` itself (so all HttpApi paths automatically install ALS). That reran the inner Effect on a detached fiber via `Effect.runPromiseExit`, which broke fiber scoping and timed out unrelated tests. Reverted.
• Refactoring the `WorkspaceAdapter` interface to be Effect-native is a cleaner long-term fix but a larger surgery. Plugin-registered adapters expect the current Promise-based shape.
• The surgical bridge installs ALS only at the existing Effect→JS boundary and keeps the adapter contract unchanged.

Followups

• Consider Effectifying the `WorkspaceAdapter` contract so this bridge can disappear.
• Consider moving more JS adapter call sites (worktree adapter create flow, workspace proxy) onto `EffectBridge.adapterPromise` so they all share the same ALS guarantees.