workflow: total, contained rendering of hostile thrown script values

Codex code-review round 2: errorText() read .stack/.message as plain property
gets and fell back to String(error) — a script throwing a value with a
throwing accessor (or toString/Symbol.toPrimitive) ran realm code in drive()'s
catch and made WorkflowRun.result REJECT, which the detached workflow/end hook
turned into an unhandledRejection (process death under dsh-app-boot).

Replaced with describeThrown in dsh-workflow-vm/realm: total (never throws),
proxy-labelling before any inspection, own-descriptor reads, String() only on
primitives, and a CONTAINED stack-getter invocation — modern V8 (Node >= 22)
makes stack an own ACCESSOR on genuine Errors, so refusing all accessors would
lose every real stack and the lineOffset line numbers; a hostile getter's
throw is swallowed and rendering falls back to message. The meta-literal
eval catch had the same String(error) exposure and now uses the same renderer.

Regression tests: a hostile-thrown-values table through the real engine
(throwing stack/message getters, data stack, setter-only stack, proxy,
Symbol.toPrimitive, function, null) asserting result resolves 'error' with the
expected rendering and NO unhandledRejection fires; a meta-path hostile throw
mapping to META_INVALID.

packages/workflow/workflow-vm/tests/meta.spec.ts

@@ -116,6 +116,13 @@ return 2`
     expect(error.message).toContain('proxies cannot cross')
   })
 
+  it('a meta expression THROWING a hostile value maps to META_INVALID — rendering runs no realm code', () => {
+    const error = bad('export const meta = { name: (() => { throw { get stack() { throw new Error("boom") }, toString() { throw new Error("boom") } } })(), description: "d" }\nreturn 1')
+    expect(error.code).toBe('META_INVALID')
+    expect(error.message).toContain('pure literal')
+    expect(error.message).toContain('[object Object]')
+  })
+
   it('rejects shape violations with EVERY violation listed (META_INVALID)', () => {
     const error = bad('export const meta = { description: 7, bogus: 1 }\nreturn 1')
     expect(error.code).toBe('META_INVALID')