Improve ACPX adapter configuration (#5290)

## Thinking Path

> - Paperclip orchestrates AI agents across several adapter
implementations.
> - ACPX is a local adapter path that can proxy Claude and Codex-style
execution.
> - Its configuration needed stronger schema defaults, provider-aware
model handling, and better UI support.
> - Plugin authors also need clear docs for managed resources.
> - This pull request improves ACPX adapter configuration and documents
plugin-managed resources.
> - The benefit is a more predictable adapter setup path without
changing unrelated control-plane behavior.

## What Changed

- Improved ACPX config schema, execution config handling, UI build
config, and route coverage.
- Added ACPX model filtering support and tests.
- Updated the agent config form and storybook coverage for ACPX
model/provider behavior.
- Expanded plugin authoring documentation for managed resources.

## Verification

- `pnpm install --frozen-lockfile`
- `pnpm exec vitest run server/src/__tests__/acpx-local-execute.test.ts
server/src/__tests__/adapter-routes.test.ts
ui/src/lib/acpx-model-filter.test.ts`

## Risks

- Low-to-medium risk: adapter configuration behavior changes can affect
ACPX users, but the change is isolated to ACPX/plugin-doc surfaces and
covered by targeted adapter tests.

## Model Used

- OpenAI GPT-5 Codex via Paperclip `codex_local` adapter, with
shell/git/GitHub CLI tool use.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

ui/storybook/stories/acpx-local.stories.tsx

@@ -43,27 +43,6 @@ const acpxLocalConfigSchema: AdapterConfigSchema = {
       type: "text",
       hint: "Required for custom agents; optional override for built-in Claude or Codex ACP commands.",
     },
-    {
-      key: "mode",
-      label: "Session mode",
-      type: "select",
-      default: "persistent",
-      options: [
-        { value: "persistent", label: "Persistent" },
-        { value: "oneshot", label: "One shot" },
-      ],
-    },
-    {
-      key: "permissionMode",
-      label: "Permission mode",
-      type: "select",
-      default: "approve-all",
-      options: [
-        { value: "approve-all", label: "Approve all" },
-        { value: "default", label: "ACP default" },
-      ],
-      hint: "Defaults to maximum permissions: ACPX permission requests are auto-approved.",
-    },
     {
       key: "nonInteractivePermissions",
       label: "Non-interactive permissions",
@@ -73,6 +52,7 @@ const acpxLocalConfigSchema: AdapterConfigSchema = {
         { value: "deny", label: "Deny" },
         { value: "fail", label: "Fail" },
       ],
+      hint: "Fallback if the ACP agent asks for input outside an interactive session. Paperclip still auto-approves permissions by default.",
     },
     {
       key: "cwd",
@@ -87,14 +67,21 @@ const acpxLocalConfigSchema: AdapterConfigSchema = {
       hint: "Optional ACPX session state directory. Defaults to Paperclip-managed company/agent scoped storage.",
     },
     {
-      key: "instructionsFilePath",
-      label: "Instructions file",
-      type: "text",
-      hint: "Optional absolute path to markdown instructions injected into the run prompt.",
+      key: "fastMode",
+      label: "Codex fast mode",
+      type: "toggle",
+      default: false,
+      hint: "Only applies when ACP agent is Codex. Requests Codex Fast mode through ACP session config.",
+      meta: { visibleWhen: { key: "agent", values: ["codex"] } },
     },
-    { key: "promptTemplate", label: "Prompt template", type: "textarea" },
-    { key: "bootstrapPromptTemplate", label: "Bootstrap prompt template", type: "textarea" },
     { key: "timeoutSec", label: "Timeout seconds", type: "number", default: 0 },
+    {
+      key: "warmHandleIdleMs",
+      label: "Warm process idle ms",
+      type: "number",
+      default: 0,
+      hint: "Defaults to 0, which closes the ACPX process after each run while retaining persistent session state.",
+    },
     {
       key: "env",
       label: "Environment JSON",