feat(cli)!: complete --config on every surface and delete the personal overlay

$DSH_HOME/config.yaml was an implicit composition layer: if the file existed,
every launch applied an arbitrary Loader patch graph over the shipped tree,
kept live by a dedicated HMR watcher. Three costs came from the implicitness,
not the capability. A patch replaces its target row's whole config, so a file
written months ago pins that row to the field set it knew and every default
the shipped tree later adds silently stops applying. It competed with the
typed settings namespaces llm-deepseek and llm-pi-ai already register, so
which one wins was a function of layer order rather than meaning. And the
explicit escape hatch it was supposedly redundant with did not exist on every
surface: dsh -p, dsh meta, and dsh upgrade all rejected --config, so for them
the implicit file was the only composition route at all.

Complete the explicit layer first: --config and --config-replace now work on
every booting surface. A headless --config-replace tree must still mount a
webserver row, because that surface reaches its own agent over the same HTTP
gateway the browser uses; AppCLIEntry names that contract in the failure
instead of reporting a bare missing service.

Then delete the implicit one. PERSONAL_CONFIG_FILENAME, loadPersonalPatches,
watchPersonalPatches, and the config-only HMR row mounted for it are gone; a
file left at that path is inert, and --dump-config no longer reads the Harness
home. --config therefore stops *replacing* the personal overlay and simply
*is* the user overlay.

No migration: a user who wants the old behavior names the same file
(dsh --config ~/.dsh/config.yaml), which a shell alias makes permanent.

examples/mcp-memory/README.zh.md

@@ -42,7 +42,7 @@ dsh --config "${DSH_HOME:-$HOME/.dsh}/memory.cordis.yml"
 
 若要选择另外任一配置，请将 URL 中的 `memorix.cordis.yml` 替换为对应文件名。运行下载的 overlay 前，请先审阅其内容：Cordis 配置可以包含可执行的 `!!js` 表达式。
 
-如果要把所选配置保存在个人配置中，请将对应文件中的单个 `insert` patch 合并到 `$DSH_HOME/config.yaml`（通常是 `~/.dsh/config.yaml`）。不要覆盖已有文件，其中可能已经包含无关的个人 patch。
+如果要跨多次运行保留所选配置，请把对应文件中的单个 `insert` patch 合并到你自己的覆盖文件里，并在每次启动时点名它（`dsh --config ~/.dsh/mcp.yml`）。不要覆盖已有的覆盖文件，其中可能已经包含无关的 patch。
 
 ## 提供方设置