fix(acp): server crashed on connect — drop export default, read optional service cwd-independently

Two independent bugs made the ACP server crash the moment an editor (Zed)
connected, despite 178 green unit tests at 100% coverage:

1. `session/new` threw `cannot get property "agents" without inject`. Root
   cause: a stray `export default apply` made the cordis Loader's
   `unwrapExports` (`exports.default ?? exports`) collapse the module to the
   bare `apply` function, discarding the sibling `inject`/`name`/`Config`
   named exports. The plugin fiber was built with empty `inject`, so every
   `ctx.<service>` read in `apply` threw at load. Fix: remove the default
   export so the Loader uses the namespace.

2. `session/load` threw `cannot get property "sessionPersistence" without
   inject`. `AgentLoop.resume` read `this.ctx.sessionPersistence` (a service
   it deliberately does NOT inject); the property proxy's ancestor-only fiber
   walk fails through the bridge's traceable shadow. Fix: read it via
   `this.ctx.get('sessionPersistence', false)`, the topology-independent
   global-store lookup.

Why the suite missed both: every test mounted the plugin by hand
(`ctx.plugin({name,inject,apply})`), bypassing `unwrapExports` entirely, and
the only test driving these RPCs was key-gated (skipped in CI). Added a no-key
`session/new` e2e that boots the real example through the real Loader — it
fails loudly on bug #1 without an API key. Set `TSX_TSCONFIG_PATH` in the e2e
spawn so the subprocess resolves workspace `paths` from a temp cwd (it was
silently falling back to a stale built `lib/`).

Docs: post-mortem 0001; AGENTS.md "line coverage is not behavior coverage" +
with-key/smoke-test philosophy; packages/AGENTS.md plugin-export-shape and
ctx.get rules; dsh-code-review SKILL checks.

packages/agent-loop/src/index.ts

@@ -152,12 +152,20 @@ export class AgentLoop extends Service implements AgentFactory {
    * by the time this runs the service exists.
    */
   async resume(options: ResumeAgentOptions): Promise<Agent> {
-    const persistence = this.ctx.sessionPersistence
-    // `sessionPersistence` is declaration-merged onto Context as non-optional,
-    // but the service is only present when a backend plugin is loaded — and
-    // AgentLoop deliberately does NOT inject it (that would pend non-persistent
-    // demos forever). So the runtime value can be undefined; the type cannot.
-    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+    // Read the service through `ctx.get(name, false)` — a direct global-store
+    // lookup keyed by the isolate symbol — NOT `this.ctx.sessionPersistence`.
+    // AgentLoop deliberately does NOT inject `sessionPersistence` (injecting it
+    // would pend non-persistent demos forever). The property proxy resolves a
+    // service by walking the current fiber's parent chain; from AgentLoop's own
+    // fiber (which lacks the inject) that walk never reaches the sibling backend
+    // fiber and throws "cannot get property … without inject". Worse, when the
+    // call arrives via a traceable shadow (e.g. the ACP bridge child fiber →
+    // `ctx.agents.resume()` → `this.factory.resume()`), the walk starts at the
+    // SHADOW's root fiber and fails the same way. `ctx.get(…, false)` sidesteps
+    // the fiber walk entirely (the same bypass the proxy itself takes when
+    // `!ctx.fiber.runtime`), so resume works from any caller fiber. `false`
+    // skips the ACTIVE-state check, since the backend lives on another fiber.
+    const persistence = this.ctx.get('sessionPersistence', false)
     if (persistence === undefined) {
       throw new Error('cannot resume: session persistence is not configured (load a dsh-session-persistence backend)')
     }