refactor(cli)!: one shared base config with per-surface overlays

`dsh` shipped two config trees that were 43 rows the same: apps/cli/cordis.yml
composed web as 74 flat rows, while the TUI booted examples/tui-agent/cordis.yml
whose single `@deepseek-ai/dsh-tui-demo` row mounted twelve plugins behind a
twenty-key pass-through Config. Neither file was what its location claimed —
apps/cli hardcoded the "example" as the product default and the "demo" bundle
was the application — and every capability change had to be made twice.

- apps/cli/base.cordis.yml holds the 43 shared rows; tui.cordis.yml and
  web.cordis.yml are patch lists stating only what differs per surface
- overlays apply as SIBLING patch lists at one include level, because include
  patches never cross an include boundary. Precedence: base < surface <
  (--config | personal ~/.dsh/config.yaml) < launcher flag/profile patches
- `--config` now applies an overlay INSTEAD OF the personal one, so a demo or
  test tree never inherits the user's route; new `--config-replace` boots a file
  as the entire tree (the old `--config` behaviour). Both survive /resume
- vendor/include: index each `insert`ed row as it is added so a later patch can
  configure or disable it. Upstream built the id index once before the patch
  loop, leaving every surface-only row — the whole TUI front door — silently
  unpatchable from user config. Logged as local modification 8
- session identity moves to dsh-agent-loop's CONFIGURED_AGENT_IDENTITIES_KEY;
  dsh-tui's MAIN_SESSION_ID_KEY is deleted (only the bundle read it)
- delete examples/tui-agent, examples/cordis-agent, packages/examples/tui-demo;
  TUI tests → apps/cli/tests, cordis e2e → packages/cordis/tool-cordis/tests,
  examples/code-mode survives as an overlay leaf
- `dsh web` gains --config, threaded into AppCLIEntry as an extra overlay

Three latent defects surfaced and are fixed here: the TUI captured the optional
sessionQuery service once at construction and could permanently disable /resume
when it won the mount race; the session-store root silently reverted to a
project-local ./.sessions; --config-replace was dropped by the resume handoff.

Verified by booting each tree through the real Loader (TUI 55 entries, web 75,
zero unsettled) rather than reading YAML. All eight terminal snapshots replay
byte-identically; 14/14 PTY smoke, 112/112 snapshots, 25/25 doc-sync, hygiene
and lint clean.

apps/cli/src/args.ts

@@ -11,10 +11,15 @@
 
 import { Command, CommanderError } from 'commander'
 
-/** Interactive TUI: the default mode. `--config` swaps the tree; `--resume <id>` rehydrates a session. */
+/**
+ * Interactive TUI: the default mode. `--config` applies an overlay over the
+ * shipped composition in place of the personal one, `--config-replace` boots a
+ * file as the whole tree instead, and `--resume <id>` rehydrates a session.
+ */
 interface TuiInvocation {
   mode: 'tui'
   config?: string
+  configReplace?: string
   resume?: string
 }
 
@@ -69,6 +74,8 @@ interface ListSessionsInvocation {
  */
 interface WebInvocation {
   mode: 'web'
+  /** Overlay of loader patches applied over the shipped web composition. */
+  config?: string
   host?: string
   port?: number
   dev: boolean
@@ -88,6 +95,7 @@ export type DshInvocation =
 
 /** Raw web-subcommand options straight from Commander. */
 interface WebOptions {
+  config?: string
   host?: string
   port?: string
   dev?: boolean
@@ -104,6 +112,7 @@ interface WebOptions {
 function resolveWeb(options: WebOptions): WebInvocation {
   return {
     mode: 'web',
+    ...options.config !== undefined && { config: options.config },
     ...options.host !== undefined && { host: options.host },
     ...options.port !== undefined && { port: Number(options.port) },
     dev: options.dev === true,
@@ -140,15 +149,16 @@ Examples:
     // subcommand without a positional collision.
     .option('-p, --prompt <task>', 'answer this task without the interactive UI, then exit')
     .option('--resume <id>', 'continue a past session by id (list ids with `dsh ps`)')
-    .option('--config <path>', 'start with an alternate plugin configuration file')
-    .action((options: { config?: string; prompt?: string; resume?: string }) => {
+    .option('--config <path>', 'apply this overlay of loader patches instead of the personal one')
+    .option('--config-replace <path>', 'boot this file as the entire tree, ignoring the shipped and personal configuration')
+    .action((options: { config?: string; configReplace?: string; prompt?: string; resume?: string }) => {
       if (options.prompt !== undefined) {
         // A headless prompt owns the invocation; an empty task has nothing to
         // run, and --config/--resume are TUI inputs that must not silently
         // vanish from a headless run.
         if (options.prompt === '') program.error('error: --prompt needs a task')
-        if (options.config !== undefined || options.resume !== undefined) {
-          program.error('error: --prompt takes no --config or --resume')
+        if (options.config !== undefined || options.configReplace !== undefined || options.resume !== undefined) {
+          program.error('error: --prompt takes no --config, --config-replace, or --resume')
         }
         resolved = { mode: 'headless', prompt: options.prompt }
         return
@@ -156,9 +166,15 @@ Examples:
       // An empty --resume= id would silently start a fresh session downstream
       // (agent-loop treats '' as no-resume), so a mistyped resume must fail loud.
       if (options.resume === '') program.error('error: --resume needs a session id')
+      // The two config flags are mutually exclusive: one layers over the shipped
+      // tree, the other discards it, so accepting both would silently drop one.
+      if (options.config !== undefined && options.configReplace !== undefined) {
+        program.error('error: --config and --config-replace are mutually exclusive')
+      }
       resolved = {
         mode: 'tui',
         ...options.config !== undefined && { config: options.config },
+        ...options.configReplace !== undefined && { configReplace: options.configReplace },
         ...options.resume !== undefined && { resume: options.resume },
       }
     })
@@ -168,8 +184,9 @@ Examples:
   // a leaked `--config`/`-p`/`--resume` is a mistyped invocation that must fail
   // loud rather than silently run and drop the input.
   const rejectParentOptions = (command: string): void => {
-    const parent = program.opts<{ config?: string; prompt?: string; resume?: string }>()
-    if (parent.config !== undefined || parent.prompt !== undefined || parent.resume !== undefined) {
+    const parent = program.opts<{ config?: string; configReplace?: string; prompt?: string; resume?: string }>()
+    if (parent.config !== undefined || parent.configReplace !== undefined
+      || parent.prompt !== undefined || parent.resume !== undefined) {
       program.error(`error: ${command} takes none of --config, -p/--prompt, or --resume`)
     }
   }
@@ -208,6 +225,7 @@ Examples:
   // would duplicate a fact this file does not own.
   const web = program.command('web').description('serve the browser UI on the configured host and port')
   web
+    .option('--config <path>', 'apply this overlay of loader patches over the shipped configuration')
     .option('--host <host>', 'bind host; pass 0.0.0.0 to reach it from another machine')
     .option('--port <port>', 'listen port; pass 0 to let the OS pick a free one')
     .option('--dev', 'developer mode: hot-reload the browser client')