feat(cli): launch dsh source through the tsx ESM hook

Node 26.0.0 removed --experimental-transform-types, so the native
source-launch chain cannot start anywhere on that line, and strip-only
mode rejects the vendored syntax (parameter properties, decorators,
runtime enums/namespaces). Switch bin/dsh, the root dsh/demo:tui/
demo:web scripts, and the Code Mode TUI overlay to node --import
tsx/esm: one launch vector across the whole engines range, ~0.4s faster
than the full tsx default (the CJS hook stays off; the graph is
ESM-only).

Delete scripts/tspath-loader.ts and apps/cli/src/tsconfig-paths-loader.ts:
tsx owns both transformation and tsconfig paths projection. Add
dsh-source-launch-smoke to the node-compat gates so the 22.19/26 matrix
executes the real launch vector; no CI job did, which is how the Node 26
breakage shipped silently.

Supersedes the native-TypeScript-source-launch Agent Note (new note
records the profiling evidence and rejected alternatives).

scripts/demo-code-mode.mjs

@@ -8,9 +8,8 @@ import { spawn } from 'node:child_process'
 // Each UI's node invocation matches its base demo script plus the overlay config.
 const UIS = new Map([
   ['tui', [
-    '--experimental-transform-types',
     '--import',
-    './scripts/tspath-loader.ts',
+    'tsx/esm',
     'apps/cli/src/bin.ts',
     '--config',
     'examples/tui-agent/code-mode.cordis.yml',

scripts/run-gates.ts

@@ -287,6 +287,11 @@ function nodeCompatSmokeGates(): Gate[] {
       'run',
       'packages/session-persistence/session-persistence-jsonl/tests/zstd.compat.spec.ts',
     ], { label: 'JSONL Zstandard smoke' }),
+    pnpmExec('dsh-source-launch-smoke', [
+      'vitest',
+      'run',
+      'apps/cli/tests/source-launch.compat.spec.ts',
+    ], { label: 'dsh source-launch smoke' }),
   ]
 }
 

scripts/tspath-loader.ts

@@ -1,14 +0,0 @@
-/** Register source-only tsconfig paths resolution before a TypeScript entry loads. */
-
-import { register } from 'node:module'
-import { resolve } from 'node:path'
-import { fileURLToPath } from 'node:url'
-
-const tsconfigPath = process.env.TSX_TSCONFIG_PATH === undefined
-  ? fileURLToPath(new URL('../tsconfig.json', import.meta.url))
-  : resolve(process.env.TSX_TSCONFIG_PATH)
-
-register(new URL('../apps/cli/src/tsconfig-paths-loader.ts', import.meta.url), {
-  parentURL: import.meta.url,
-  data: { tsconfigPath },
-})