fix(web-config): close the wire boundary, the redacted-replace data loss, and three P2s

Five findings from the #939 review, each reproduced before being fixed.

**Configuration reads are as privileged as writes.** `settings.describe`
returns every exposed namespace's configuration and `credentials.describe`
reports whether an arbitrary environment-variable name is configured and from
where — reconnaissance no anonymous caller should have. Both join
PRIVILEGED_METHODS, so the whole configuration plane is loopback-only until
real authentication exists; `trustedHosts` was never authentication. The model
catalog stays reachable: it carries no endpoints or key state, and a LAN
client's model picker legitimately needs it. Asserted over a real HTTP server,
because the Host header a browser actually sends is what decides this.

**The proxy serves only namespaces a registered model provider addresses.**
The settings seam is general — any plugin may register one — but the Web
configuration plane is the model-provider surface. Without the gate, every
future `settings.register()` would silently become remotely readable and
writable configuration. An unregistered namespace and an unexposed one answer
identically, so no caller can enumerate the registry one probe at a time.

**Path-addressed writes replace the redacted-document rebuild.** The editor
reads the REDACTED descriptor, so rebuilding a section from it and replacing
wholesale deleted every literal secret the wire never returned — reproduced as
`{baseURL, reasoning}` in, stored `apiKey` gone out. `settings.mutate` applies
set/unset ops to the section as it stands at the front of the seam's write
queue, and the client names only fields it can see, so an unseen secret is
untouched by construction rather than by care.

P2s in the same pass: `llm/adapters-updated` now contains async listener
rejections (an uncontained one escaped as unhandledRejection, contradicting
the documented "observer failures are contained"); llm-deepseek's retry-policy
swap uses the atomic `registration.replace` instead of dispose-then-register,
which published `[]` then `["deepseek-official"]` so an observer saw the
provider disappear and come back; and a transport rejection no longer strands
the page in `loading` or a card in `busy`, with removal failures surfaced on
the page banner instead of swallowed.

packages/llm/llm-deepseek/src/index.ts

@@ -220,16 +220,17 @@ export function apply(ctx: Context, config: Config): void {
   ])
   // Route effects bind to this apply fiber via the stable `ctx` reference,
   // even when a swap runs inside the scoped settings callback below.
-  let disposeRoute = ctx.llm.registerAdapter([PROVIDER], adapter)
+  const registration = ctx.llm.registerAdapter([PROVIDER], adapter)
   let registeredPolicy = options().retryPolicy
   const ensureRegistrationFacts = (): void => {
     const policy = options().retryPolicy
     if (deepEqualJson(policy, registeredPolicy)) return
     // The registry captures the retry policy at registration, so it is the one
-    // fact per-request resolution cannot refresh: swap the registration in one
-    // synchronous section (same adapter instance, no NO_ADAPTER window).
-    disposeRoute()
-    disposeRoute = ctx.llm.registerAdapter([PROVIDER], adapter)
+    // fact per-request resolution cannot refresh. `replace` re-reads it in one
+    // synchronous registry section: disposing and re-registering instead would
+    // publish an empty route set between the two, and an observer that reacted
+    // to it would see this provider disappear and come back.
+    registration.replace([PROVIDER])
     registeredPolicy = policy
   }
 

packages/llm/llm-deepseek/tests/dynamic-config.spec.ts

@@ -113,10 +113,18 @@ describe('request-level dynamic configuration', () => {
     ])
   })
 
-  it('re-registers the route in place when the captured retry policy changes', async () => {
+  it('re-registers the route in place when the captured retry policy changes, without an empty-registry window', async () => {
     const dir = await home()
     const { ctx } = await boot(dir, { apiKey: 'k', baseURL: 'http://127.0.0.1:1' })
 
+    // Observing the topology event, not just the end state: disposing and
+    // re-registering also lands on the right final registry, but publishes an
+    // empty route set in between, so an observer sees the provider disappear.
+    const observed: string[][] = []
+    ctx.on('llm/adapters-updated', () => {
+      observed.push(ctx.llm.listProviders().map(provider => provider.id))
+    })
+
     await ctx.settings.update(NS, {
       retryPolicy: { mode: 'always', backoff: { initialDelayMs: 25, maxDelayMs: 100, jitterRatio: 0.2 } },
     })
@@ -127,6 +135,7 @@ describe('request-level dynamic configuration', () => {
       jitterRatio: 0.2,
     })
     expect(ctx.llm.listProviders()).toEqual([{ id: 'deepseek-official', name: 'DeepSeek' }])
+    expect(observed).toEqual([['deepseek-official']])
   })
 
   it('keeps the last good options when a settings snapshot fails beyond-schema validation', async () => {