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.

docs/architecture.md

@@ -147,6 +147,10 @@ running, the handler exits as usual.
 
 `task` runs a nested `streamText` and returns one message. The subagent kinds hold different
 tool sets: `explore` and `review` the read-only tools, `worker` those plus every write tool.
+A `tasks` array on the call runs several of these nests concurrently — each gets its own
+context window and stream, awaited together via `Promise.all` — so independent investigations
+overlap instead of queueing. The single-prompt form is just the one-element case; the two paths
+share the same nested-loop machinery and the same reporting bus.
 
 The consequences follow from the tool set, not from policy: