v5.0.6

### Inline Self-Review Replaces Subagent Review Loops

The subagent review loop (dispatching a fresh agent to review plans/specs) doubled execution time (~25 min overhead) without measurably improving plan quality. Regression testing across 5 versions with 5 trials each showed identical quality scores regardless of whether the review loop ran.

- **brainstorming** — replaced Spec Review Loop (subagent dispatch + 3-iteration cap) with inline Spec Self-Review checklist: placeholder scan, internal consistency, scope check, ambiguity check
- **writing-plans** — replaced Plan Review Loop (subagent dispatch + 3-iteration cap) with inline Self-Review checklist: spec coverage, placeholder scan, type consistency
- **writing-plans** — added explicit "No Placeholders" section defining plan failures (TBD, vague descriptions, undefined references, "similar to Task N")
- Self-review catches 3-5 real bugs per run in ~30s instead of ~25 min, with comparable defect rates to the subagent approach

### Brainstorm Server

- **Session directory restructured** — the brainstorm server session directory now contains two peer subdirectories: `content/` (HTML files served to the browser) and `state/` (events, server-info, pid, log). Previously, server state and user interaction data were stored alongside served content, making them accessible over HTTP. The `screen_dir` and `state_dir` paths are both included in the server-started JSON. (Reported by 吉田仁)

### Bug Fixes

- **Owner-PID lifecycle fixes** — the brainstorm server's owner-PID monitoring had two bugs causing false shutdowns within 60 seconds: (1) EPERM from cross-user PIDs (Tailscale SSH, etc.) was treated as "process dead", and (2) on WSL the grandparent PID resolves to a short-lived subprocess that exits before the first lifecycle check. Fixed by treating EPERM as "alive" and validating the owner PID at startup — if it's already dead, monitoring is disabled and the server relies on the 30-minute idle timeout. This also removes the Windows/MSYS2-specific carve-out from `start-server.sh` since the server now handles it generically. (#879)
- **writing-skills** — corrected false claim that SKILL.md frontmatter supports "only two fields"; now says "two required fields" and links to the agentskills.io specification for all supported fields (PR #882 by @arittr)

### Codex App Compatibility

- **codex-tools** — added named agent dispatch mapping documenting how to translate Claude Code's named agent types to Codex's `spawn_agent` with worker roles (PR #647 by @arittr)
- **codex-tools** — added environment detection and Codex App finishing sections for worktree-aware skills (by @arittr)
- **Design spec** — added Codex App compatibility design spec (PRI-823) covering read-only environment detection, worktree-safe skill behavior, and sandbox fallback patterns (by @arittr)