fix(den): preserve admin capability arguments

[benjaminshafii]

Summary

Fixes admin MCP capability argument plumbing so execute_capability can call tools like admin:den_query with real input.

Reproduced error before the fix when executing admin:den_query with body {"sql":"SELECT @@sql_mode"} (and equivalently with the new regression's JSON-string body):

MCP error -32602: Input validation error: Invalid arguments for tool den_query: [
  { "expected": "string", "code": "invalid_type", "path": ["sql"],
    "message": "Invalid input: expected string, received undefined" }
]

Root cause / fix

• Defect A: ee/apps/den-api/src/mcp/admin-capabilities.ts:98-104 now uses the existing normalizeToolRecord(body) ?? {} helper from ./invoke.js; the removed local normalizeArguments helper previously returned {} for JSON-encoded string bodies, silently dropping every admin argument.
• Defect B: ee/apps/den-api/src/mcp/admin-capabilities.ts:40-63 now emits argumentsSchema: tool.inputSchema and invocation: { argumentsField: "body" } for admin tools with input, matching the external-MCP convention. ee/apps/den-api/src/mcp/search.ts:36-39 types those shared match fields.

No changes were made to admin:den_query behavior, SQL allowlisting, permission gating, or admin-tools.ts.

Regression proof

Before fix (tests added, production code still unfixed):

$ pnpm --filter @openwork-ee/den-api exec bun test test/admin-capabilities.test.ts
bun test v1.3.10 (30e609e0)

test/admin-capabilities.test.ts:
40 | 
41 |   test("forwards arguments when body is a JSON-encoded string", async () => {
42 |     const result = await adminCapabilities.executeAdminCapability("admin:den_query", JSON.stringify({ sql: "DELETE FROM user" }))
43 | 
44 |     expect(result?.isError).toBe(true)
45 |     expect(contentText(result)).toContain("Only SELECT/WITH/SHOW/DESCRIBE/EXPLAIN statements are allowed")
                                     ^
error: expect(received).toContain(expected)

Expected to contain: "Only SELECT/WITH/SHOW/DESCRIBE/EXPLAIN statements are allowed"
Received: "MCP error -32602: Input validation error: Invalid arguments for tool den_query: [\n  {\n    \"expected\": \"string\",\n    \"code\": \"invalid_type\",\n    \"path\": [\n      \"sql\"\n    ],\n    \"message\": \"Invalid input: expected string, received undefined\"\n  }\n]"

      at <anonymous> (/Users/benjaminshafii/openwork-enterprise/_repos/_worktrees/openwork-admin-capability-args/ee/apps/den-api/test/admin-capabilities.test.ts:45:33)
(fail) executeAdminCapability > forwards arguments when body is a JSON-encoded string [2.24ms]
68 |       throw new Error("Expected admin:den_query match to be a record")
69 |     }
70 | 
71 |     const argumentsSchema = match.argumentsSchema
72 |     if (!isRecord(argumentsSchema) || !isRecord(argumentsSchema.properties)) {
73 |       throw new Error("Expected admin:den_query to expose an object argumentsSchema")
                     ^
error: Expected admin:den_query to expose an object argumentsSchema
      at <anonymous> (/Users/benjaminshafii/openwork-enterprise/_repos/_worktrees/openwork-admin-capability-args/ee/apps/den-api/test/admin-capabilities.test.ts:73:17)
(fail) searchAdminCapabilities > exposes argumentsSchema for tools that take input [4.42ms]

 2 pass
 2 fail
 8 expect() calls
Ran 4 tests across 1 file. [147.00ms]
undefined
/Users/benjaminshafii/openwork-enterprise/_repos/_worktrees/openwork-admin-capability-args/ee/apps/den-api:
[ERR_PNPM_RECURSIVE_EXEC_FIRST_FAIL] Command failed with exit code 1: bun test test/admin-capabilities.test.ts

After fix:

$ NO_COLOR=1 pnpm --filter @openwork-ee/den-api exec bun test test/admin-capabilities.test.ts
bun test v1.3.10 (30e609e0)

test/admin-capabilities.test.ts:
2026-07-25T11:44:43.546Z WARN [Better Auth]: Please ensure '/.well-known/oauth-authorization-server/api/auth' exists. Upon completion, clear with silenceWarnings.oauthAuthServerConfig.

 4 pass
 0 fail
 10 expect() calls
Ran 4 tests across 1 file. [457.00ms]

Affected tests:

$ NO_COLOR=1 pnpm --filter @openwork-ee/den-api exec bun test test/admin-capabilities.test.ts test/admin-mcp.test.ts test/admin-mcp-routes.test.ts
bun test v1.3.10 (30e609e0)

test/admin-capabilities.test.ts:
2026-07-25T11:44:50.660Z WARN [Better Auth]: Please ensure '/.well-known/oauth-authorization-server/api/auth' exists. Upon completion, clear with silenceWarnings.oauthAuthServerConfig.

 19 pass
 0 fail
 49 expect() calls
Ran 19 tests across 3 files. [450.00ms]

Typecheck:

$ pnpm --filter @openwork-ee/den-api exec tsc -p tsconfig.json --noEmit
# exited 0 with no output

Other commands run:

$ pnpm --filter @openwork-ee/den-db build
# passed; needed because this fresh worktree had no den-db dist files for Bun's default workspace export resolution

$ pnpm --filter @openwork/email build
# passed; needed after importing invoke.ts because Bun resolves @openwork/email to dist in this local setup

$ git diff --check
# exited 0 with no output

No video/fraimz is included because this is an MCP argument-plumbing fix with no UI surface. The real end-to-end proof after deploy is admin:den_query accepting {"sql": "..."} through execute_capability.

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Project	Deployment	Actions	Updated (UTC)
openwork-app	Ready	Preview, Comment	Jul 25, 2026 11:45am
openwork-den	Ready	Preview, Comment	Jul 25, 2026 11:45am
openwork-den-worker-proxy	Ready	Preview, Comment	Jul 25, 2026 11:45am
openwork-landing	Ready	Preview, Comment, Open in v0	Jul 25, 2026 11:45am

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
openwork-diagnostics	Skipped		Jul 25, 2026 11:45am