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.

CHANGELOG.md

@@ -4,6 +4,38 @@ All notable changes to this project are documented here. The format follows
 [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) and the project adheres to
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+A batch of loop and ergonomics work landed after 1.0.0. Version remains `1.0.0` in
+`src/version.ts`; these are folded into the next tagged release.
+
+### Added
+
+- **`/undo` and `/redo`.** Every prompt snapshots the files on disk first (capped near the last
+  100), and `/undo` restores files, trims the conversation, or both. `/redo` reverses it. A
+  `bash` command's side effects are not files and cannot be rolled back, which is stated in the
+  command output rather than hidden.
+- **Parallel subagents.** The `task` tool accepts several independent investigations under a
+  `tasks` array and runs them on separate context windows at the same time, joining their
+  reports. A single call behaves exactly as before.
+- **Lazy MCP tools.** By default an MCP server now contributes three meta-tools (`mcp_list`,
+  `mcp_inspect`, `mcp_call`) instead of one schema per server tool, so a server exposing twenty
+  tools stops costing ~2750 tokens per request until one is actually called. Set
+  `"mcpMode": "eager"` to register every server tool up front. Named servers are still listed
+  in the prompt, and calls route through the same permission rules and guard as before.
+- **Hot-reloaded skill installs.** A skill installed from `/registry` mid-session is callable
+  on the next turn without a restart (the `skill` tool reads its list live, so even the first
+  install works). Plugins and external tools still need a restart because they join the guard
+  chain and tool registry built once at boot.
+
+### Fixed
+
+- The walk behind `@file` completion refreshed only once per session; it now re-walks on a slow
+  cooldown so a file created after the first `@` shows up within a short window.
+- A handful of plugin write tools were mutating but not gated by the permission defaults; the
+  tool set and the mutating list are now derived from a single `mutating()` marker, so a tool
+  can no longer be added to one and forgotten in the other.
+
 ## [1.0.0]
 
 The first stable release. Cost control, a larger tool and skill surface, custom slash