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/rigor/dsl-compiler.test.js

@@ -23,7 +23,7 @@
 import { describe, it } from 'node:test';
 import assert from 'node:assert/strict';
 import { rigor } from '@rigor/core';
-import { DSLCompiler } from '../../src/ast/DSLCompiler.js';
+import { DSLCompiler } from '@arbiter/evidence-dsl/DSLCompiler';
 
 // Built-in types from lib/src/ast/validation/DSLPrelude.js are reserved (User, Account,
 // Device, AuthSession). Use non-reserved names so the validator accepts the DSL.
@@ -215,8 +215,8 @@ describe('DSLCompiler → engine rule mapping (rigor)', () => {
       // multi_hop shape uses a plain variable binding instead. We bypass the
       // validator by directly exercising the parser→generator path: parse
       // only, then run the generator against the parsed AST.
-      const { parse } = await import('../../src/ast/parser/DSLParser.js');
-      const { RuleGenerator } = await import('../../src/ast/generator/RuleGenerator.js');
+      const { parse } = await import('@arbiter/evidence-dsl/parser/DSLParser');
+      const { RuleGenerator } = await import('@arbiter/evidence-dsl/generator/RuleGenerator');
       const dsl = `${DEFINITIONS}${FACTS}\nevidence canReach(a: Person, b: Person) { friend_of(a, f) { friend_of(f, b) } limit 5 }\n`;
       const program = parse(dsl);
       const generator = new RuleGenerator(arbiter);

tests/rigor/dsl-mutation-parity.test.js

@@ -17,7 +17,7 @@ import { describe, it } from 'node:test';
 import assert from 'node:assert/strict';
 import { rigor } from '@rigor/core';
 import { Arbiter } from '../../src/index.js';
-import { DSLCompiler } from '../../src/ast/DSLCompiler.js';
+import { DSLCompiler } from '@arbiter/evidence-dsl/DSLCompiler';
 
 const EPS = 1e-9;
 const POS = [0, 0.25, 0.5, 0.75, 1];

tests/rigor/zanzibar-defeasible-dsl-comparator.test.js

@@ -20,7 +20,7 @@ import { describe, it } from 'node:test';
 import assert from 'node:assert/strict';
 import { rigor } from '@rigor/core';
 import { Arbiter } from '../../src/index.js';
-import { DSLCompiler } from '../../src/ast/DSLCompiler.js';
+import { DSLCompiler } from '@arbiter/evidence-dsl/DSLCompiler';
 
 const EPS = 1e-9;
 const POSSIBILITIES = [0, 0.25, 0.5, 0.75, 1];