refactor(cli): unify the arg grammar — one program, --config flag, real web subcommand

Drop the bare `dsh <config>` positional in favor of a `--config <path>` flag.
Without a root positional, `web` can be a real Commander subcommand in one
program instead of the reserved-first-token dispatch to a second parser, so
`dsh --help` lists every mode natively (no hand-pasted command text) and the
second parser + reserved-token machinery are gone.

Grammar:
  dsh                       TUI (shipped tree + ~/.dsh overlay)
  dsh --config <path>       TUI, alternate tree (demos/tests only)
  dsh --resume <id>         TUI, resume a session
  dsh -p "task"             headless one-shot
  dsh web [--host --port --dev]

`dsh` is the product front door with no positional; `--config` exists only so
demo:cordis, demo:code-mode, and the keyless PTY smokes can point the shipped
bin at an example tree. Those three sites and the /resume re-exec argv move to
`--config <path>`. The `-p` + `--config`/`--resume` mode-mixing guard and the
cordis.yml-owns-host/port-default fix are preserved.

Agent Note + Chinese pair, README, tui.ts docs updated. All 13 PTY smokes
(including code-mode via --config and the exec-replace resume handoff) green.

vitest.e2e.config.ts

@@ -38,7 +38,9 @@ export default defineConfig({
   plugins: [tsconfigPaths({ projects: ['./tsconfig.base.json'] })],
   test: {
     setupFiles: ['./scripts/test-invariants.ts'],
-    include: ['packages/*/*/tests/**/*.e2e.ts', 'apps/*/tests/**/*.e2e.ts', 'examples/*/tests/**/*.e2e.ts'],
+    // apps/cli only, not apps/*: apps/web/tests/*.e2e.ts needs the built
+    // frontend dist and runs under vitest.web.config.ts (the test:web job).
+    include: ['packages/*/*/tests/**/*.e2e.ts', 'apps/cli/tests/**/*.e2e.ts', 'examples/*/tests/**/*.e2e.ts'],
     // Real model calls: generous timeouts, and retries for transient flakes
     // (the shared internal key hits concurrency quotas). No coverage — the
     // unit suites own the coverage gate.