feat(adapters): add capability flags to ServerAdapterModule (#3540)

## Thinking Path

> - Paperclip orchestrates AI agents via adapters (`claude_local`,
`codex_local`, etc.)
> - Each adapter type has different capabilities — instructions bundles,
skill materialization, local JWT — but these were gated by 5 hardcoded
type lists scattered across server routes and UI components
> - External adapter plugins (e.g. a future `opencode_k8s`) cannot add
themselves to those hardcoded lists without patching Paperclip source
> - The existing `supportsLocalAgentJwt` field on `ServerAdapterModule`
proves the right pattern already exists; it just wasn't applied to the
other capability gates
> - This pull request replaces the 4 remaining hardcoded lists with
declarative capability flags on `ServerAdapterModule`, exposed through
the adapter listing API
> - The benefit is that external adapter plugins can now declare their
own capabilities without any changes to Paperclip source code

## What Changed

- **`packages/adapter-utils/src/types.ts`** — added optional capability
fields to `ServerAdapterModule`: `supportsInstructionsBundle`,
`instructionsPathKey`, `requiresMaterializedRuntimeSkills`
- **`server/src/routes/agents.ts`** — replaced
`DEFAULT_MANAGED_INSTRUCTIONS_ADAPTER_TYPES` and
`ADAPTERS_REQUIRING_MATERIALIZED_RUNTIME_SKILLS` hardcoded sets with
capability-aware helper functions that fall back to the legacy sets for
adapters that don't set flags
- **`server/src/routes/adapters.ts`** — `GET /api/adapters` now includes
a `capabilities` object per adapter (all four flags + derived
`supportsSkills`)
- **`server/src/adapters/registry.ts`** — all built-in adapters
(`claude_local`, `codex_local`, `process`, `cursor`) now declare flags
explicitly
- **`ui/src/adapters/use-adapter-capabilities.ts`** — new hook that
fetches adapter capabilities from the API
- **`ui/src/pages/AgentDetail.tsx`** — replaced hardcoded `isLocal`
allowlist with `capabilities.supportsInstructionsBundle` from the API
- **`ui/src/components/AgentConfigForm.tsx`** /
**`OnboardingWizard.tsx`** — replaced `NONLOCAL_TYPES` denylist with
capability-based checks
- **`server/src/__tests__/adapter-registry.test.ts`** /
**`adapter-routes.test.ts`** — tests covering flag exposure,
undefined-when-unset, and per-adapter values
- **`docs/adapters/creating-an-adapter.md`** — new "Capability Flags"
section documenting all flags and an example for external plugin authors

## Verification

- Run `pnpm test --filter=@paperclip/server -- adapter-registry
adapter-routes` — all new tests pass
- Run `pnpm test --filter=@paperclip/adapter-utils` — existing tests
still pass
- Spin up dev server, open an agent with `claude_local` type —
instructions bundle tab still visible
- Create/open an agent with a non-local type — instructions bundle tab
still hidden
- Call `GET /api/adapters` and verify each adapter includes a
`capabilities` object with the correct flags

## Risks

- **Low risk overall** — all new flags are optional with
backwards-compatible fallbacks to the existing hardcoded sets; no
adapter behaviour changes unless a flag is explicitly set
- Adapters that do not declare flags continue to use the legacy lists,
so there is no regression risk for built-in adapters
- The UI capability hook adds one API call to AgentDetail mount; this is
a pre-existing endpoint, so no new latency path is introduced

## Model Used

- Provider: Anthropic
- Model: Claude Sonnet 4.6 (`claude-sonnet-4-6`)
- Context: 200k token context window
- Mode: Agentic tool use (code editing, bash, grep, file reads)

## 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 run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] 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: Pawla Abdul (Bot) <pawla@groombook.dev>
Co-authored-by: Paperclip <noreply@paperclip.ing>

packages/adapter-utils/src/types.ts

@@ -328,6 +328,36 @@ export interface ServerAdapterModule {
    * resolved inside this method — the caller receives a fully hydrated schema.
    */
   getConfigSchema?: () => Promise<AdapterConfigSchema> | AdapterConfigSchema;
+
+  // ---------------------------------------------------------------------------
+  // Adapter capability flags
+  //
+  // These allow adapter plugins to declare what "local" capabilities they
+  // support, replacing hardcoded type lists in the server and UI.
+  // All flags are optional — when undefined, the server falls back to
+  // legacy hardcoded lists for built-in adapters.
+  // ---------------------------------------------------------------------------
+
+  /**
+   * Adapter supports managed instructions bundle (AGENTS.md files).
+   * When true, the server uses instructionsPathKey (default "instructionsFilePath")
+   * to resolve the instructions config key, and the UI shows the bundle editor.
+   * Built-in local adapters default to true; external plugins must opt in.
+   */
+  supportsInstructionsBundle?: boolean;
+
+  /**
+   * The adapterConfig key that holds the instructions file path.
+   * Defaults to "instructionsFilePath" when supportsInstructionsBundle is true.
+   */
+  instructionsPathKey?: string;
+
+  /**
+   * Adapter needs runtime skill entries materialized (written to disk)
+   * before being passed via config. Used by adapters that scan a directory
+   * rather than reading config.paperclipRuntimeSkills.
+   */
+  requiresMaterializedRuntimeSkills?: boolean;
 }
 
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