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>

packages/adapters/acpx-local/src/index.ts

@@ -1,3 +1,5 @@
+import type { AdapterModel } from "@paperclipai/adapter-utils";
+
 export const type = "acpx_local";
 export const label = "ACPX (local)";
 
@@ -6,6 +8,7 @@ export const DEFAULT_ACPX_LOCAL_MODE = "persistent";
 export const DEFAULT_ACPX_LOCAL_PERMISSION_MODE = "approve-all";
 export const DEFAULT_ACPX_LOCAL_NON_INTERACTIVE_PERMISSIONS = "deny";
 export const DEFAULT_ACPX_LOCAL_TIMEOUT_SEC = 0;
+export const DEFAULT_ACPX_LOCAL_WARM_HANDLE_IDLE_MS = 0;
 
 export const acpxAgentOptions = [
   { id: "claude", label: "Claude via ACPX" },
@@ -13,6 +16,8 @@ export const acpxAgentOptions = [
   { id: "custom", label: "Custom ACP command" },
 ] as const;
 
+export const models: AdapterModel[] = [];
+
 export const agentConfigurationDoc = `# acpx_local agent configuration
 
 Adapter: acpx_local
@@ -30,7 +35,7 @@ Don't use when:
 Core fields:
 - agent (string, optional): claude, codex, or custom. Defaults to claude.
 - agentCommand (string, optional): custom ACP command when agent=custom, or an override for a built-in ACP agent command.
-- mode (string, optional): persistent or oneshot. Defaults to persistent.
+- mode (string, optional): persistent or oneshot. Defaults to persistent. Paperclip keeps session state persistent and may close the live process between runs.
 - cwd (string, optional): default absolute working directory fallback for the agent process.
 - permissionMode (string, optional): defaults to approve-all, meaning ACPX permission requests are auto-approved.
 - nonInteractivePermissions (string, optional): fallback behavior when ACPX cannot ask interactively. Supported values are deny and fail.
@@ -38,7 +43,11 @@ Core fields:
 - instructionsFilePath (string, optional): absolute path to a markdown instructions file used by Paperclip prompt construction.
 - promptTemplate (string, optional): run prompt template.
 - bootstrapPromptTemplate (string, optional): first-run bootstrap prompt template.
+- model (string, optional): requested ACP model. Claude and Codex ACP agents both receive this through ACP session config.
+- effort/modelReasoningEffort (string, optional): requested thinking effort. Claude uses effort; Codex uses modelReasoningEffort/reasoning_effort.
+- fastMode (boolean, optional): for ACPX Codex, request Codex fast mode through ACP session config.
 - timeoutSec (number, optional): run timeout in seconds. Defaults to 0, meaning no adapter timeout.
+- warmHandleIdleMs (number, optional): live ACPX process idle window after a successful persistent run. Defaults to 0, meaning Paperclip shuts the process down after each run while retaining ACPX session state.
 - env (object, optional): KEY=VALUE environment variables or secret bindings.
 
 Dependency decision: