refactor: extract Evidence DSL to @arbiter/evidence-dsl package

The Evidence DSL (ADR-000) compiles a natural DSL into core rule
configurations — it is a separate concern from the engine. The AST had
zero runtime coupling to the core (DSLCompiler takes the arbiter as a
duck-typed argument; ip-utils were the only shared code, now local to
the DSL package). This extraction removes the DSL surface from the core
artifact entirely:

- src/ast/ (748K, ~60 files) moved to @arbiter/evidence-dsl@1.0.0
- ip-utils moved with it (only the DSL consumed them)
- generate-parser script + peggy devDep moved to the DSL package
- the 8 DSL-consuming tests now import from @arbiter/evidence-dsl
  (deep-path exports: DSLCompiler, parser/*, generator/*, validation/*,
  interpreter/*)
- package.json gains the devDependency, drops build:ast/generate:parser

Tarball: AST-free. Rigor 251/251, full suite 838/776/0.

tests/rules/dsl-injectable-predicate.test.js

@@ -1,6 +1,6 @@
 import { describe, test } from 'node:test';
 import assert from 'node:assert/strict';
-import { validateDslText } from '../../src/ast/validation/DSLValidation.js';
+import { validateDslText } from '@arbiter/evidence-dsl/validation/DSLValidation';
 
 describe.skip('DSL injectable predicates (* prefix)', () => {
   test('allows injectable predicates with * prefix in evidence bodies', () => {

tests/rules/pipe-e-filter-e2e.test.js

@@ -1,5 +1,5 @@
-import { parse } from '../../src/ast/parser/GeneratedParser.js';
-import { RuleGenerator } from '../../src/ast/generator/RuleGenerator.js';
+import { parse } from '@arbiter/evidence-dsl/parser/GeneratedParser';
+import { RuleGenerator } from '@arbiter/evidence-dsl/generator/RuleGenerator';
 import { Arbiter } from '../../src/core/Arbiter.js';
 
 const dsl = [