fix(cli)!: stop hoisting $DSH_HOME/.env into process.env

The shipped surfaces loaded the harness home's .env into the process
environment before cordis booted. credentials-local then saw every stored
key as an ambient launch override: describe reported source 'env' with
writable false, and set/unset rejected as shadowed — so a key the web page
or TUI stored was unrotatable and undeletable from the next run onward,
and the adapter kept using the value captured at launch.

The home's .env is now the credential provider's own store, read by that
provider alone and hot-reloaded by it. The genuine launch environment and
the invoking directory's .env (loaded by the bin) remain the read-only
ambient layer, so a plain composition without the provider still resolves
keys exactly as before.

Proven by a real restart in the loader composition: store a key through
the seam, dispose the tree, re-boot over the same harness home, and the
entry is still file-sourced and writable — rotating it lands on the very
next request.

apps/cli/src/tui.ts

@@ -1,9 +1,10 @@
 /**
  * `dsh` default surface — the interactive TUI coding agent. Boots the shipped
  * tui-agent config (or the `--config` override) with the personal overlay
- * from the Harness home (`~/.dsh`): its `.env` fills environment gaps (precedence:
- * ambient environment, then the invoking directory's `.env`, then the personal one)
- * and its `config.yaml` patches the booted tree. The workspace is the invoking
+ * from the Harness home (`~/.dsh`): its `config.yaml` patches the booted tree.
+ * The environment layers are the ambient one and the invoking directory's
+ * `.env`; `$DSH_HOME/.env` stays the credential provider's own store and is
+ * never hoisted into `process.env`. The workspace is the invoking
  * directory: sessions, relative paths, and workspace instructions resolve from
  * the cwd, so `dsh` acts on whatever project it is launched in. After boot, the
  * agent's system prompt is told the path to this harness checkout so it can find
@@ -17,12 +18,10 @@ import {
   addHarnessSourceSection,
   boot,
   installFailLoud,
-  loadEnv,
   loadPersonalPatches,
   RESUME_SESSION_ID_KEY,
   resolveConfigPath,
 } from '@deepseek-ai/dsh-app-boot'
-import { resolveDshHome } from '@deepseek-ai/dsh-paths'
 import type { Context } from 'cordis'
 import {
   TUI_GOODBYE_MESSAGE_KEY,
@@ -63,9 +62,11 @@ export async function runTui(config: string | undefined, resumeSessionId: string
     process.exit(1)
   }
   installFailLoud(NAME)
-  // The bin already loaded the invoking directory's .env; the personal .env
-  // only fills what is still unset (process.loadEnvFile never overrides).
-  loadEnv(NAME, resolveDshHome())
+  // The bin already loaded the invoking directory's .env as the ambient
+  // layer. `$DSH_HOME/.env` is deliberately NOT loaded here: it is the
+  // credential provider's own writable store, and hoisting it into
+  // process.env would make every stored key look like a read-only launch
+  // override on the next run, blocking rotation from the TUI and the web page.
   process.env.DSH_BUNDLED_SKILL_DIR = join(SOURCE_ROOT, 'skills')
   // The in-place `/resume` handoff re-execs `dsh` with a normalized `--resume`
   // flag, so the resumed process rehydrates through this same intake. The host