feat(config)!: one ordering for configuration sources, and a bootstrap deny rule

$DSH_HOME/.env had just become an ordinary environment layer, which left the
harness resolving user-facing values from a flattened process.env that could
no longer say where a value came from. A key stored through the web page
stayed shadowed by an older key in the user's own .env. An endpoint could be
redirected by the project: the invoking directory's .env is materialized like
every other layer, and a base URL decides where a resolved API key is sent, so
a DEEPSEEK_BASE_URL written into a model-editable workspace would send the
user's credential — and the prompts carrying their code — to whatever host
that file named.

Give every user-facing value one ordering, with four kinds of source:

  explicit for this run     per-operation override, CLI argument
  > authored by deployment  --config / --config-replace
  > this launch's shell     inherited process environment
  > product-managed store   settings.yaml, .credentials.yaml
  > discovered file         $DSH_HOME/.env
  > defaults                schema default, shipped base, public default

The domains differ only in which tiers exist. The earlier split — credentials
ranking the environment over the managed file while settings ranked over the
environment — was inconsistent: the distinguishing fact is who authored the
source, not the domain.

packages/util/environment owns an immutable snapshot with per-layer
provenance. getFrom(name, sources) searches only the layers a caller names,
and omitting one is a refusal rather than a demotion: the adapters ask for
['process', 'user-env'], so no reordering can let a project file back into a
decision it was excluded from.

isBootstrapOnly rejects, before anything is materialized, any .env setting a
variable that governs how a process launches (PATH, SHELL, NODE_OPTIONS,
LD_PRELOAD), where code or model-visible instructions load from (the whole
DSH_* namespace, HOME, XDG_*), or how the network is reached (proxy and CA
variables). The namespace is denied wholesale so a switch added later cannot
become settable by being forgotten, and there is no opt-out.

verify-config-source-ownership keeps both rules: no unregistered process.env
read under packages/*/*/src (26 allowlisted with reasons), and no apiKey,
baseURL, or headers inlined from the environment in shipped Cordis config —
removing those inlines is what makes the deployment tier meaningful.

apps/cli/src/bin.ts

@@ -24,24 +24,27 @@ function readVersion(): string {
   return typeof manifest.version === 'string' ? manifest.version : '0.0.0'
 }
 
-loadLayeredEnv('dsh')
+const environment = loadLayeredEnv('dsh')
 // The env opt-in is read at the process boundary; `1` is the documented value.
 const invocation = parseDshArgs(process.argv.slice(2), readVersion(), process.env.DSH_EXPERIMENTAL === '1')
 
 switch (invocation.mode) {
   case 'web': {
     const { runWeb } = await import('./web.ts')
-    await runWeb(invocation.host, invocation.port, invocation.dev, invocation.workspaceRoot, invocation.trustedHosts, invocation.config)
+    await runWeb(
+      environment, invocation.host, invocation.port, invocation.dev,
+      invocation.workspaceRoot, invocation.trustedHosts, invocation.config,
+    )
     break
   }
   case 'headless': {
     const { runHeadless } = await import('./headless.ts')
-    await runHeadless(invocation.prompt, invocation.config, invocation.configReplace)
+    await runHeadless(environment, invocation.prompt, invocation.config, invocation.configReplace)
     break
   }
   case 'tui': {
     const { runTui } = await import('./tui.ts')
-    await runTui(invocation.config, invocation.resume, undefined, undefined, invocation.configReplace)
+    await runTui(environment, invocation.config, invocation.resume, undefined, undefined, invocation.configReplace)
     break
   }
   case 'dump-config': {
@@ -51,12 +54,12 @@ switch (invocation.mode) {
   }
   case 'meta': {
     const { runTui, SOURCE_ROOT } = await import('./tui.ts')
-    await runTui(invocation.config, undefined, SOURCE_ROOT, undefined, invocation.configReplace)
+    await runTui(environment, invocation.config, undefined, SOURCE_ROOT, undefined, invocation.configReplace)
     break
   }
   case 'upgrade': {
     const { runTui } = await import('./tui.ts')
-    await runTui(invocation.config, undefined, undefined, `dsh-${invocation.mode}`, invocation.configReplace)
+    await runTui(environment, invocation.config, undefined, undefined, `dsh-${invocation.mode}`, invocation.configReplace)
     break
   }
   default: