feat(model-overlays): add fable-5 overlay + resolver mapping

Give claude-fable-5 a dedicated overlay instead of the generic claude
fallback: inherits the claude base plus Fable-family nudges (act when
ready, ground progress claims, assessment-vs-action, delegate). Adds the
models.ts resolver mapping and a gate-tier test mirroring the opus overlays.

model-overlays/fable-5.md

@@ -0,0 +1,23 @@
+{{INHERIT:claude}}
+
+**Act when you have enough to act.** Fable 5 can over-plan on ambiguous tasks.
+When you have enough information to act, act. Do not re-derive facts already
+established in the conversation, re-litigate a decision the user has already made,
+or narrate options you will not pursue in user-facing messages. Give a
+recommendation, not an exhaustive survey. This does not apply to thinking blocks.
+
+**Ground progress claims in evidence.** Before reporting progress, audit each
+claim against a tool result from this session. Report only work you can point to;
+if something is not yet verified, say so. If tests fail, say so with the output;
+if a step was skipped, say that; when something is done and verified, state it
+plainly without hedging.
+
+**Assessment vs action.** When the user is describing a problem, asking a
+question, or thinking out loud rather than requesting a change, the deliverable is
+your assessment: report findings and stop. Don't apply a fix until they ask. Before
+a state-changing command (restart, delete, config edit), confirm the evidence
+supports that specific action.
+
+**Delegate independent work.** When a task fans out across independent items,
+delegate to sub-agents and keep working while they run, rather than iterating
+serially. Intervene if a sub-agent goes off track or is missing context.

scripts/models.ts

@@ -14,6 +14,7 @@
 export const ALL_MODEL_NAMES = [
   'claude',
   'opus-4-7',
+  'fable-5',
   'gpt',
   'gpt-5.4',
   'gemini',
@@ -53,6 +54,7 @@ export function resolveModel(input: string): Model | null {
   if (/^gpt(-|$)/.test(s)) return 'gpt';
   if (/^o[0-9]+(-|$)/.test(s)) return 'o-series';
   if (/^claude-opus-4-7(-|$)/.test(s)) return 'opus-4-7';
+  if (/^claude-fable-5(-|$)/.test(s)) return 'fable-5';
   if (/^claude(-|$)/.test(s)) return 'claude';
   if (/^gemini(-|$)/.test(s)) return 'gemini';
 

test/model-overlay-fable-5.test.ts

@@ -0,0 +1,55 @@
+/**
+ * Fable 5 model overlay — gate-tier assertions on the family nudges.
+ *
+ * fable-5 inherits the claude base and adds Fable-family nudges: act when you
+ * have enough context (avoid over-planning), ground progress claims in tool
+ * results, assessment-vs-action boundaries, and delegate independent work.
+ */
+import { describe, test, expect } from 'bun:test';
+import * as fs from 'fs';
+import * as path from 'path';
+import type { TemplateContext } from '../scripts/resolvers/types';
+import { HOST_PATHS } from '../scripts/resolvers/types';
+import { generateModelOverlay } from '../scripts/resolvers/model-overlay';
+
+function makeCtx(model: string): TemplateContext {
+  return {
+    skillName: 'test-skill',
+    tmplPath: 'test.tmpl',
+    host: 'claude',
+    paths: HOST_PATHS.claude,
+    preambleTier: 2,
+    model,
+  };
+}
+
+const ROOT = path.resolve(__dirname, '..');
+
+describe('Fable 5 overlay — family nudges', () => {
+  test('raw fable-5.md contains the act-when-ready nudge', () => {
+    const raw = fs.readFileSync(path.join(ROOT, 'model-overlays/fable-5.md'), 'utf-8');
+    expect(raw).toContain('Act when you have enough to act');
+  });
+
+  test('resolved overlay inherits from claude base (INHERIT:claude)', () => {
+    const out = generateModelOverlay(makeCtx('fable-5'));
+    expect(out).toContain('Todo-list discipline');
+    expect(out).toContain('subordinate');
+  });
+
+  test('resolved overlay carries the Fable nudges', () => {
+    const out = generateModelOverlay(makeCtx('fable-5'));
+    expect(out).toContain('Act when you have enough to act');
+    expect(out).toContain('Ground progress claims in evidence');
+  });
+
+  test('resolved overlay has no unresolved INHERIT directive', () => {
+    const out = generateModelOverlay(makeCtx('fable-5'));
+    expect(out).not.toContain('{{INHERIT:');
+  });
+
+  test('claude overlay (base) does not carry the Fable nudge', () => {
+    const out = generateModelOverlay(makeCtx('claude'));
+    expect(out).not.toContain('Act when you have enough to act');
+  });
+});