Retire the readline front door and the repl-agent example

Delete packages/ui/stdio and examples/repl-agent; rename stdio-demo to
@deepseek-ai/dsh-tui-demo (TUI-only, refuses pipes before Loader boot).
tui-agent owns the coding composition inline; echo-agent and the CI demo
smoke move to the one-shot cli-demo bin, which gains -p/--prompt. The
UI-independent with-key e2es move verbatim to tui-agent. SDK wizard's
'stdio' interface becomes 'tui'. PTY testing stays confined to TUI
surfaces; all other subprocess tests ride pipes.

See .agents/notes/implemented/simplification/2026-07-20-retire-readline-front-door.md

knip.json

@@ -55,7 +55,8 @@
       "project": ["src/**/*.ts", "tests/**/*.ts"]
     },
     "packages/util/brand": {
-      "project": ["src/**/*.ts"]
+      "project": ["src/**/*.ts"],
+      "ignoreDependencies": ["cordis"]
     },
     "packages/util/timeout": {
       "entry": ["tests/**/*.spec.ts"],
@@ -142,7 +143,7 @@
       "project": ["src/**/*.ts", "tests/**/*.ts"]
     },
     "packages/examples/tui-demo": {
-      "entry": ["tests/**/*.spec.ts"],
+      "entry": ["tests/**/*.spec.ts", "tests/**/*.e2e.ts"],
       "project": ["src/**/*.ts", "tests/**/*.ts"]
     },
     "packages/examples/cli-demo": {