fix(core): accept string commands in workspace hook config

[christso]

Summary

• Workspace hook command now accepts a string (e.g., command: node scripts/setup.mjs) by auto-splitting on whitespace
• Previously, string commands were silently ignored — parseWorkspaceScriptConfig returned undefined with no warning

Test plan

• New test: should accept string command and auto-split on whitespace
• All 21 workspace config parsing tests pass
• All 1187 core tests pass
• Pre-push hooks (build, typecheck, lint, test, validate) all pass

Red/Green UAT

Test YAML — suite defines a default hook with array syntax; one test case tries to override it with string syntax:

workspace:
  hooks:
    before_all:
      command: ["node", "default-setup.mjs"]

tests:
  - id: uses-default
    input: "Hello"
    criteria: "Should work"
  - id: custom-override
    input: "Hello"
    criteria: "Should work"
    workspace:
      hooks:
        before_all:
          command: node custom-setup.mjs

Reproduction command (from repo root):

bun -e "
import { loadTests } from './packages/core/src/evaluation/yaml-parser.js';
const cases = await loadTests('/tmp/subtle-test.yaml', '/tmp');
for (const c of cases) {
  console.log(c.id + ':', JSON.stringify(c.workspace?.hooks?.before_all?.command));
}
"

RED (on main) — override silently falls back to suite default

uses-default: ["node","default-setup.mjs"]
custom-override: ["node","default-setup.mjs"]   ← wrong! should be custom-setup.mjs

The string command is silently ignored, so custom-override inherits the suite-level default. The user thinks their custom hook ran, but it didn't.

GREEN (on fix/778-string-command) — override works correctly

uses-default: ["node","default-setup.mjs"]
custom-override: ["node","custom-setup.mjs"]     ← correct

Closes #778

🤖 Generated with Claude Code

[cloudflare-workers-and-pages]

Deploying agentv with    Cloudflare Pages

Latest commit:	a3d2781
Status:	✅  Deploy successful!
Preview URL:	https://c8aabe3a.agentv.pages.dev
Branch Preview URL:	https://fix-778-string-command.agentv.pages.dev

View logs