perf(resolution): drop non-unique edge indexes during the bulk resolution window, byte-identical graphs (#1322)

The resolution persist's measured cost is B-tree maintenance on the edges
table's five indexes (offline replay of a 224k-edge resolution set: 2.8s with
all indexes, 1.1s with only the unique identity index, +0.3s to recreate the
rest). On big runs (same >=150k-ref gate as the resolver pool) the four
non-unique edge indexes are now dropped for the batch loop and recreated in
one pass each before synthesis.

Why this is safe:
- idx_edges_identity stays: INSERT OR IGNORE's dedup conflicts on it (#1034),
  and its leftmost column is `source`, so the only mid-window edge reads —
  resolution's supertype walks (implements/extends by source) — keep an index
  via its prefix (verified with EXPLAIN QUERY PLAN).
- The window closes BEFORE synthesis, whose passes read kind-keyed, and on
  every error path (finally).
- A crash inside the window heals on the next DatabaseConnection open —
  schema.sql re-applies CREATE INDEX IF NOT EXISTS, same recovery as the FTS
  bulk-load pattern this mirrors.
- Concurrent readers (a daemon serving the project mid-index) stay correct;
  target/kind-keyed reads degrade to scans only for the window's duration.

dubbo (4,402 files): persists 4.0s -> 3.0s, fresh init 11.9s -> ~11.1s,
graph byte-identical. excalidraw (below the gate): untouched, byte-identical.
Recreation cost ~250ms, logged under CODEGRAPH_SYNTH_TIMINGS as
edge-index-recreate. Suite green (2444).

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/index.ts

@@ -1149,6 +1149,15 @@ export class CodeGraph {
   ): Promise<ResolutionResult> {
     return this.resolver.resolveAndPersistBatched(onProgress, undefined, onSynthesisProgress, {
       dbPath: this.db.getPath(),
+      // Bulk-edge-load hooks: on big runs the resolver drops the non-unique
+      // edge indexes for the batch loop and recreates them before synthesis
+      // (which reads kind-keyed). Concurrent readers (a daemon serving this
+      // project mid-index) stay CORRECT during the window — target/kind reads
+      // just degrade to scans until the recreate.
+      bulkEdgeLoad: {
+        begin: () => this.db.beginBulkEdgeLoad(),
+        end: () => this.db.endBulkEdgeLoad(),
+      },
     });
   }