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.

docs/user/guide/config.md

@@ -50,7 +50,7 @@ Plugins load in file order. Place plugins that depend on services after the appl
 
 ## CLI overlays
 
-The TUI composes `base.cordis.yml` and `tui.cordis.yml`, then applies one optional patch list. By default that final list is `~/.dsh/config.yaml`; `dsh --config <path>` replaces the personal list with the named overlay. `dsh --config-replace <path>` instead boots the named file as the complete tree, without shipped or personal layers. `dsh web --config <path>` adds its overlay after the shared base and Web surface defaults and before the Web launcher's CLI-flag patches.
+The TUI composes `base.cordis.yml` and `tui.cordis.yml`, then applies the optional `dsh --config <path>` overlay. `dsh --config-replace <path>` instead boots the named file as the complete tree, without any shipped layer. Every booting surface takes both flags — `dsh -p`, `dsh web`, `dsh meta`, and `dsh upgrade` included — because naming a file is the only way to compose your own tree.
 
 A patch replaces a row's entire `config` value; it does not deep-merge keys. For example, patching `llm-deepseek` with only `config: { thinking: disabled }` also removes that row's configured `apiKey` and `baseURL`, so restate every key the row must retain.