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>

server/src/routes/agents.ts

@@ -72,6 +72,8 @@ import {
 import { getTelemetryClient } from "../telemetry.js";
 
 export function agentRoutes(db: Db) {
+  // Legacy hardcoded maps — used as fallback when adapter module does not
+  // declare capability flags explicitly.
   const DEFAULT_INSTRUCTIONS_PATH_KEYS: Record<string, string> = {
     claude_local: "instructionsFilePath",
     codex_local: "instructionsFilePath",
@@ -83,6 +85,22 @@ export function agentRoutes(db: Db) {
     pi_local: "instructionsFilePath",
   };
   const DEFAULT_MANAGED_INSTRUCTIONS_ADAPTER_TYPES = new Set(Object.keys(DEFAULT_INSTRUCTIONS_PATH_KEYS));
+
+  /** Check if an adapter supports the managed instructions bundle. */
+  function adapterSupportsInstructionsBundle(adapterType: string): boolean {
+    const adapter = findActiveServerAdapter(adapterType);
+    if (adapter?.supportsInstructionsBundle !== undefined) return adapter.supportsInstructionsBundle;
+    return DEFAULT_MANAGED_INSTRUCTIONS_ADAPTER_TYPES.has(adapterType);
+  }
+
+  /** Resolve the adapter config key for the instructions file path. */
+  function resolveInstructionsPathKey(adapterType: string): string | null {
+    const adapter = findActiveServerAdapter(adapterType);
+    if (adapter?.instructionsPathKey) return adapter.instructionsPathKey;
+    if (adapter?.supportsInstructionsBundle === true) return "instructionsFilePath";
+    if (adapter?.supportsInstructionsBundle === false) return null;
+    return DEFAULT_INSTRUCTIONS_PATH_KEYS[adapterType] ?? null;
+  }
   const KNOWN_INSTRUCTIONS_PATH_KEYS = new Set(["instructionsFilePath", "agentsMdPath"]);
   const KNOWN_INSTRUCTIONS_BUNDLE_KEYS = [
     "instructionsBundleMode",
@@ -557,7 +575,7 @@ export function agentRoutes(db: Db) {
     adapterType: string;
     adapterConfig: unknown;
   }>(agent: T): Promise<T> {
-    if (!DEFAULT_MANAGED_INSTRUCTIONS_ADAPTER_TYPES.has(agent.adapterType)) {
+    if (!adapterSupportsInstructionsBundle(agent.adapterType)) {
       return agent;
     }
 
@@ -638,7 +656,9 @@ export function agentRoutes(db: Db) {
     };
   }
 
-  const ADAPTERS_REQUIRING_MATERIALIZED_RUNTIME_SKILLS = new Set([
+  // Legacy hardcoded set — used as fallback when adapter module does not
+  // declare requiresMaterializedRuntimeSkills explicitly.
+  const LEGACY_MATERIALIZED_SKILLS_SET = new Set([
     "cursor",
     "gemini_local",
     "opencode_local",
@@ -646,7 +666,11 @@ export function agentRoutes(db: Db) {
   ]);
 
   function shouldMaterializeRuntimeSkillsForAdapter(adapterType: string) {
-    return ADAPTERS_REQUIRING_MATERIALIZED_RUNTIME_SKILLS.has(adapterType);
+    const adapter = findActiveServerAdapter(adapterType);
+    if (adapter?.requiresMaterializedRuntimeSkills !== undefined) {
+      return adapter.requiresMaterializedRuntimeSkills;
+    }
+    return LEGACY_MATERIALIZED_SKILLS_SET.has(adapterType);
   }
 
   async function buildRuntimeSkillConfig(
@@ -1617,7 +1641,7 @@ export function agentRoutes(db: Db) {
 
     const existingAdapterConfig = asRecord(existing.adapterConfig) ?? {};
     const explicitKey = asNonEmptyString(req.body.adapterConfigKey);
-    const defaultKey = DEFAULT_INSTRUCTIONS_PATH_KEYS[existing.adapterType] ?? null;
+    const defaultKey = resolveInstructionsPathKey(existing.adapterType);
     const adapterConfigKey = explicitKey ?? defaultKey;
     if (!adapterConfigKey) {
       res.status(422).json({