Ship the batch: undo, parallel subagents, lazy MCP, hot-reloaded skills; docs and CI/CD

Loop and ergonomics batch across Now/Next and Maintenance:
- /undo and /redo via pre-prompt file snapshots (snapshot.ts)
- task takes a tasks[] array and runs investigations concurrently (subagent.ts)
- lazy MCP tools: mcp_list/mcp_inspect/mcp_call meta-tools, eager opt-in (mcp.ts, config.ts)
- skill tool reads its list live so a mid-session install is callable next turn (skills.ts)
- tool-name lists (tool-kinds.ts) derived from a mutating() marker; gates previously ungated writes
- prune/session recovery path summarized, and step-back doom-loop primitive (step-back.ts)
- @file completion re-walks on a slow cooldown; estimateTokens and pricing labeled as estimates

Docs: README, CHANGELOG, docs/{mcp,architecture,development} updated to match.
CI/CD: bun install-store cache and concurrency gates on both workflows; release.yml now
composes file-based release notes via scripts/make-release-notes.ts and verifies every binary.

test/commit.test.ts

@@ -1,7 +1,7 @@
-import { usageOf } from './helpers';
+import { generateResult, streamOf, textChunks, usageOf } from './helpers';
 import { afterEach, beforeEach, expect, test } from 'bun:test';
-import { MockLanguageModelV4, simulateReadableStream } from 'ai/test';
-import type { LanguageModelV4CallOptions, LanguageModelV4StreamPart } from '@ai-sdk/provider';
+import { MockLanguageModelV4 } from 'ai/test';
+import type { LanguageModelV4CallOptions } from '@ai-sdk/provider';
 import { mkdtempSync, rmSync } from 'node:fs';
 import { tmpdir } from 'node:os';
 import { join } from 'node:path';
@@ -15,16 +15,7 @@ import { GIT_TOOL_NAMES } from '../src/tools-git';
 
 const usage = usageOf(10);
 
-const stream = (parts: LanguageModelV4StreamPart[]) => ({
-  stream: simulateReadableStream({ chunks: parts, chunkDelayInMs: null, initialDelayInMs: null }),
-});
-
-const text = (body: string): LanguageModelV4StreamPart[] => [
-  { type: 'text-start', id: '0' },
-  { type: 'text-delta', id: '0', delta: body },
-  { type: 'text-end', id: '0' },
-  { type: 'finish', finishReason: { unified: 'stop', raw: 'stop' }, usage },
-];
+const text = (body: string) => textChunks(body, usage);
 
 let dir: string;
 let origCwd: string;
@@ -69,16 +60,11 @@ function recordingModel(
   const model = new MockLanguageModelV4({
     doStream: async (o) => {
       seen.push(o);
-      return stream(text(reply));
+      return streamOf(text(reply));
     },
     doGenerate: async (o) => {
       seen.push(o);
-      return {
-        content: [{ type: 'text', text: reply }],
-        finishReason: { unified: 'stop', raw: 'stop' },
-        usage,
-        warnings: [],
-      } as any;
+      return generateResult(reply, usage);
     },
   });
   return { model, seen };