fix(explore): surface synth constant-endpoint edges + precise redux-thunk dispatch resolution

Two fixes hardening the redux-thunk dynamic-dispatch synthesizer, found by
validating it on real RTK repos beyond its trezor origin (uwave-web,
session-desktop, octo-call):

- Surfacing: buildFlowFromNamedSymbols filtered its named set to CALLABLE
  kinds, so synthesized edges between `constant` nodes (RTK thunks are
  `const X = createAsyncThunk(...)`) never entered the Flow / Dynamic-dispatch
  links scan — invisible at every tier, while the kind-agnostic Relationships
  section is off below 500 files. Add a `dynNamed` set (named constant/variable/
  field nodes with a heuristic edge) feeding a shared collectSynthLinks into the
  "## Dynamic-dispatch links" section, threaded through the named.size<2
  early-out (both-endpoints-constant hit return EMPTY first) and the main path.
  Main call-chain stays callable-only; the <500 budget tiers are untouched.
  No-op for callable flows. Plus a generic synthEdgeNote fallback so any synth
  hop reads "dynamic: <kind> @site", not a bare "[calls]".

- Precision: reduxThunkEdges resolved a dispatched name by first-match-by-kind,
  so a thunk name colliding with a same-named service function linked to the
  wrong node (octo-call `leaveCall`). Prefer thunk-signature const > other
  const > same-file callable > first match.

Tests: new explore-synth-constant-endpoints.test.ts (surfacing on a small repo)
+ a collision case in redux-thunk-synthesizer.test.ts. Full suite green (1605).
Rationale + coverage backlog in docs/design/dispatch-synthesizer-backlog.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

__tests__/explore-synth-constant-endpoints.test.ts

@@ -0,0 +1,86 @@
+/**
+ * Regression: codegraph_explore must SURFACE a synthesized edge whose endpoints are
+ * `constant` nodes (RTK thunk→thunk), on a SMALL repo.
+ *
+ * `buildFlowFromNamedSymbols` historically filtered its "named" set to CALLABLE kinds
+ * (method/function/component/constructor), excluding `constant`. RTK thunks are
+ * `export const X = createAsyncThunk(...)`, so a thunk→thunk hop is constant→constant —
+ * it never entered the flow scan and surfaced nowhere on the Flow path. The kind-agnostic
+ * "### Relationships" section would have caught it, but that is disabled below 500 files.
+ * Net: on a small RTK app the synthesized edge existed in the graph yet was invisible to
+ * the agent. The fix feeds a `dynNamed` set (named non-callable endpoints that participate
+ * in a heuristic edge) to the tier-independent "## Dynamic-dispatch links" scan. This test
+ * pins it on a deliberately tiny (<150-file) fixture so the Relationships gate is OFF and
+ * the dynamic-dispatch-links path is the ONLY thing that can surface the hop.
+ */
+import { describe, it, expect, beforeAll, afterAll, afterEach } from 'vitest';
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+import * as os from 'node:os';
+import CodeGraph from '../src/index';
+import { ToolHandler } from '../src/mcp/tools';
+
+// Assertions read RAW codegraph_explore output; managed offload would replace it. Disable
+// it for this file so the suite is hermetic regardless of dev-machine config, then restore.
+let _prevOffloadDisable: string | undefined;
+beforeAll(() => { _prevOffloadDisable = process.env.CODEGRAPH_OFFLOAD_DISABLE; process.env.CODEGRAPH_OFFLOAD_DISABLE = '1'; });
+afterAll(() => {
+  if (_prevOffloadDisable === undefined) delete process.env.CODEGRAPH_OFFLOAD_DISABLE;
+  else process.env.CODEGRAPH_OFFLOAD_DISABLE = _prevOffloadDisable;
+});
+
+describe('codegraph_explore — synthesized constant→constant edges surface on small repos', () => {
+  let dir: string;
+  let cg: CodeGraph;
+  let handler: ToolHandler;
+
+  afterEach(() => {
+    if (cg) cg.destroy();
+    if (dir && fs.existsSync(dir)) fs.rmSync(dir, { recursive: true, force: true });
+  });
+
+  it('surfaces an RTK thunk→thunk hop (both `constant`) in the Dynamic-dispatch links section', async () => {
+    dir = fs.mkdtempSync(path.join(os.tmpdir(), 'explore-thunk-surface-'));
+    fs.writeFileSync(
+      path.join(dir, 'package.json'),
+      JSON.stringify({ name: 'app', dependencies: { '@reduxjs/toolkit': '^2' } })
+    );
+    fs.writeFileSync(
+      path.join(dir, 'thunks.ts'),
+      `import { createAsyncThunk } from '@reduxjs/toolkit';
+
+export const deepThunk = createAsyncThunk('app/deep', async (n: number) => n * 2);
+
+export const innerThunk = createAsyncThunk('app/inner', async (n: number, { dispatch }) => {
+  return dispatch(deepThunk(n));
+});
+
+export const outerThunk = createAsyncThunk('app/outer', async (n: number, { dispatch }) => {
+  await dispatch(innerThunk(n));
+});
+`
+    );
+
+    cg = CodeGraph.initSync(dir, { config: { include: ['**/*.ts'], exclude: [] } });
+    await cg.indexAll();
+
+    // Precondition: the endpoints really are `constant` nodes — the exact kind the old
+    // CALLABLE-only flow scan dropped (if extraction ever classed them as functions the
+    // test would pass vacuously, so assert the case we actually fixed).
+    const db = (cg as any).db.db;
+    const outerKind = db.prepare(`SELECT kind FROM nodes WHERE name = 'outerThunk' LIMIT 1`).get()?.kind;
+    expect(outerKind).toBe('constant');
+
+    handler = new ToolHandler(cg);
+    const res = await handler.execute('codegraph_explore', { query: 'outerThunk innerThunk' });
+    const text = res.content[0].text as string;
+
+    // The synthesized hop now surfaces (was invisible: both endpoints `constant` AND the
+    // small-repo Relationships section is off).
+    expect(text).toContain('## Dynamic-dispatch links among your symbols');
+    expect(text).toMatch(/outerThunk\s+→\s+innerThunk/);
+    // It reads as a dynamic-dispatch bridge with its wiring site, not a bare `calls`.
+    expect(text).toMatch(/dynamic: redux thunk @/);
+    expect(text).not.toMatch(/outerThunk\s+→\s+innerThunk\s+\[calls\]/);
+  });
+});