perf(resolution): batch-loop de-quadratic — keyset reads, changes-based guard, DB-scaled valve caps + resolve profiler (#1339)

The §7a.2 per-ref profile overturned the assumption the whole arc was
built on: resolveOne owns only ~93s of the kernel-scale ~433s batch loop.
Loop-stage attribution (CODEGRAPH_RESOLVE_PROFILE, shipped here) named the
rest: backpressure folds 111.2s, count guard 93.9s, batch reads 54.6s,
deletes/inserts/marks ~84s, settle 85.7s.

- Non-progress guard O(remaining)→O(1): the per-batch COUNT(*) walked every
  remaining pending row (O(N²/batch) per run, 93.9s). The cleanup queries
  now return summed SQLite , and zero-removals-from-claimed-work
  is the guard signal — the DIRECT evidence the count diff inferred (a
  mismatched-name resolver makes keyed cleanup no-op ⇒ changes=0). A real
  COUNT runs only on that suspicious path and arbitrates exactly as before.
- Batch reads OFFSET→keyset (54.6s→O(batch)): OFFSET re-walked the
  accumulated failed-row prefix every read; seeking past the last-seen
  rowid is prefix-independent and enumeration-order identical.
- WAL valve caps scale with DB size (env still wins): every fold re-writes
  hot pages (#1231 in bounded form — 111.2s at the flat 256MB cap);
  soft=clamp(dbSize/4, 256MB, 2GB) trades ~4× fewer folds for a transient
  WAL ≈ project size.
- CODEGRAPH_RESOLVE_PROFILE: per-outcome resolveOne histogram + loop-stage
  attribution, main + workers, off by default.

Gates: dubbo dump byte-identical; suite 2,491 passed / 4 skipped (kernel
required). Kernel-scale payoff run lands in the plan doc next.

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

src/index.ts

@@ -25,7 +25,7 @@ import {
   FindRelevantContextOptions,
 } from './types';
 import { DatabaseConnection, getDatabasePath, removeDatabaseFiles } from './db';
-import { WalCheckpointValve } from './db/wal-valve';
+import { WalCheckpointValve, resolveWalValveMb } from './db/wal-valve';
 import { QueryBuilder } from './db/queries';
 import {
   isInitialized,
@@ -472,7 +472,7 @@ export class CodeGraph {
         this.db.setWalAutocheckpoint(0);
         walValve = new WalCheckpointValve(
           this.db,
-          undefined,
+          resolveWalValveMb(process.env.CODEGRAPH_WAL_VALVE_MB, this.db.getDbFileSizeBytes()),
           undefined,
           options.verbose ? (m) => console.log(`[wal-valve] ${m}`) : undefined
         );
@@ -753,7 +753,7 @@ export class CodeGraph {
         this.db.setWalAutocheckpoint(0);
         walValve = new WalCheckpointValve(
           this.db,
-          undefined,
+          resolveWalValveMb(process.env.CODEGRAPH_WAL_VALVE_MB, this.db.getDbFileSizeBytes()),
           undefined,
           options.verbose ? (m) => console.log(`[wal-valve] ${m}`) : undefined
         );