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.

docs/testing.zh.md

@@ -46,4 +46,4 @@ e2e 断言应重新运行命令或从外部重新读取文件；对 agent 自身
 
 ## 何时需要快照测试
 
-每项非平凡的模型可见、协议可见或人类可见变更，都必须在同一 PR 中，通过可运行示例所属的快照套件添加或更新无密钥场景。包测试、e2e 断言、mock 与仅测试组合、PR 理由都不能取代组装后的 transcript；必要时应扩展 harness。ACP 自动化场景使用 `examples/<name>/tests/snapshots/`，即基于 [`dsh-acp-snapshot`](../packages/support/acp-snapshot/README.md) 套件工厂的场景表（`examples/acp-agent` 为主套件）；`examples/headless-agent` 拥有 `stream-json` 快照与回放 fixture。已完成的交互式终端旅程使用 `examples/tui-agent/tests/snapshots/` 下由 JSONL 驱动的场景；瞬态呈现使用包内语义矩阵，输入、Loader 选择或终端清理发生变化时还要添加 PTY 用例。新的能力 seam、生命周期形态或 transcript 呈现接口在计划阶段就要列出每个覆盖层级，并在实现前验证 harness 能够表达它们。
+每项非平凡的模型可见、协议可见或人类可见变更，都必须在同一 PR 中，通过可运行示例所属的快照套件添加或更新无密钥场景。包测试、e2e 断言、mock 与仅测试组合、PR 理由都不能取代组装后的 transcript；必要时应扩展 harness。ACP 自动化场景使用 `examples/<name>/tests/snapshots/`，即基于 [`dsh-acp-snapshot`](../packages/support/acp-snapshot/README.md) 套件工厂的场景表（`examples/acp-agent` 为主套件）；`examples/headless-agent` 拥有 `stream-json` 快照与回放 fixture。已完成的交互式终端旅程使用 `apps/cli/tests/snapshots/` 下由 JSONL 驱动的场景；瞬态呈现使用包内语义矩阵，输入、Loader 选择或终端清理发生变化时还要添加 PTY 用例。新的能力 seam、生命周期形态或 transcript 呈现接口在计划阶段就要列出每个覆盖层级，并在实现前验证 harness 能够表达它们。