fix(index): yield during resolution so the liveness watchdog can't kill a valid large index (#1091) (#1105)

The #850 liveness watchdog SIGKILLs a process whose main-thread event loop
stalls past its window (60s default). It was extended to `index`/`init` in
#999, but reference resolution and callback-edge synthesis run synchronously
on that same thread — so on a large repo a legitimate, in-progress index gets
killed, and users had to disable the watchdog entirely (CODEGRAPH_NO_WATCHDOG=1).

Make the long synchronous spans yield cooperatively so the heartbeat keeps
firing during real work, while a genuinely wedged span (which never reaches a
yield) still trips the watchdog:

- synthesizeCallbackEdges yields between its whole-graph passes, and the heavy
  scanners (closure-collection, event-emitter, JSX-child, object-registry,
  field-channel) yield within their loops;
- batched resolution sub-chunks each batch with yields;
- the deferred chained-call and this-member post-passes yield per ref.

Behaviour-preserving — only timing changes; node/edge counts are identical.

Validated end-to-end with the real watchdog armed at the default 60s: the
released build is SIGKILLed partway through indexing the Swift compiler (27k
files, ~1.1M edges) and the TypeScript compiler, while the fixed build indexes
both to completion.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/index.ts

@@ -473,10 +473,10 @@ export class CodeGraph {
           // receiver conforms to (protocol-extension / inherited / default-
           // interface). Needs the implements/extends edges the main pass just
           // built, so it runs after resolution (#750).
-          this.resolver.resolveChainedCallsViaConformance();
+          await this.resolver.resolveChainedCallsViaConformance();
           // Same lifecycle for `this.<member>` callback registrations whose
           // member is inherited from a supertype (#808).
-          this.resolver.resolveDeferredThisMemberRefs();
+          await this.resolver.resolveDeferredThisMemberRefs();
         }
 
         // Refresh planner stats + checkpoint the WAL after bulk writes.
@@ -597,10 +597,10 @@ export class CodeGraph {
           // Second pass: chained calls whose method lives on a supertype the
           // receiver conforms to (protocol-extension / inherited). Needs the
           // implements/extends edges built above (#750).
-          this.resolver.resolveChainedCallsViaConformance();
+          await this.resolver.resolveChainedCallsViaConformance();
           // Same lifecycle for `this.<member>` callback registrations whose
           // member is inherited from a supertype (#808).
-          this.resolver.resolveDeferredThisMemberRefs();
+          await this.resolver.resolveDeferredThisMemberRefs();
         }
 
         // Refresh planner stats + checkpoint the WAL after bulk writes.