docs: move SECURITY.md to .github/ and SPEEDRUN.md to docs/

Trims the repo root listing so the README is reached with less scrolling.
Only these two were movable; the other five root .md files are load-bearing
and stay put:

- README.md / README.zh-CN.md — the landing page and the language-switcher
  entry point
- CLAUDE.md — Claude Code loads project instructions from the ROOT path;
  moving it silently breaks every future session in this repo
- AGENTS.md — the agent-convention file Codex reads from the root and injects
  as context (see the comments in session-routes.ts)
- CHANGELOG.md — the changesets default writer emits it next to package.json,
  so moving it breaks `npm run version-packages`

GitHub officially resolves .github/SECURITY.md, so the Security policy tab
keeps working. Inbound links updated in both READMEs, CLAUDE.md and
docs/versioning-policy.md. CHANGELOG.md also names SECURITY.md but is left
alone: it is a historical record, not a live reference.

The move broke a link the other direction too: SECURITY.md pointed at
docs/security-architecture.md, which from .github/ resolved to
.github/docs/... — repointed to ../docs/. All relative links in the six
touched files verified resolving (62 links, 0 broken).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.github/SECURITY.md

@@ -4,7 +4,7 @@ Codeman launches AI coding sessions with `--dangerously-skip-permissions`, so th
 web UI is **by design a remote-code-execution surface for whoever can reach it**.
 The entire security model exists to control *who* that is. Please read this before
 exposing an instance beyond `localhost`. The full model lives in
-[`docs/security-architecture.md`](docs/security-architecture.md).
+[`docs/security-architecture.md`](../docs/security-architecture.md).
 
 ## Supported versions
 
@@ -75,4 +75,4 @@ subscribe and send time), and tmux session names discovered on the shared socket
 are validated against the safe-name pattern before reaching any shell call site.
 
 For the detailed rationale, defenses, and recommended secure setups, see
-[`docs/security-architecture.md`](docs/security-architecture.md).
+[`docs/security-architecture.md`](../docs/security-architecture.md).

CLAUDE.md

@@ -38,7 +38,7 @@ The production server caches static files for 1 year, `immutable` (`maxAge: '1y'
 
 ## COM Shorthand (Deployment)
 
-Uses [Semantic Versioning](https://semver.org/) (`MAJOR.MINOR.PATCH`) via `@changesets/cli`. What SemVer actually covers (the CLI + documented env vars are public; the HTTP/SSE API, on-disk state, and experimental features are internal/unstable) is defined in `docs/versioning-policy.md`. Security reporting + known limitations live in `SECURITY.md`.
+Uses [Semantic Versioning](https://semver.org/) (`MAJOR.MINOR.PATCH`) via `@changesets/cli`. What SemVer actually covers (the CLI + documented env vars are public; the HTTP/SSE API, on-disk state, and experimental features are internal/unstable) is defined in `docs/versioning-policy.md`. Security reporting + known limitations live in `.github/SECURITY.md`.
 
 When user says "COM":
 

README.md

@@ -604,7 +604,7 @@ When someone authenticates via QR, the desktop shows a notification toast with t
 
 ## Security
 
-By default Codeman launches sessions with `--dangerously-skip-permissions`, so the web UI is by design a remote-code-execution surface for whoever can reach it — the whole security model exists to control _who_ that is. (The startup permission mode is configurable; see below.) Recent hardening (v0.9.0 + v0.9.5) closes the browser-driven attack paths that bite self-hosted dev tools. Full model: [`docs/security-architecture.md`](docs/security-architecture.md). **Found a vulnerability?** See [`SECURITY.md`](SECURITY.md) for private disclosure and the list of known limitations.
+By default Codeman launches sessions with `--dangerously-skip-permissions`, so the web UI is by design a remote-code-execution surface for whoever can reach it — the whole security model exists to control _who_ that is. (The startup permission mode is configurable; see below.) Recent hardening (v0.9.0 + v0.9.5) closes the browser-driven attack paths that bite self-hosted dev tools. Full model: [`docs/security-architecture.md`](docs/security-architecture.md). **Found a vulnerability?** See [`SECURITY.md`](.github/SECURITY.md) for private disclosure and the list of known limitations.
 
 ### Network & access
 

README.zh-CN.md

@@ -594,7 +594,7 @@ URL 被刻意保持精简（`/q/` 路径 + 6 字符码 ≈ 53–56 个字符）
 
 ## 安全
 
-Codeman 默认用 `--dangerously-skip-permissions` 启动会话，因此 Web UI 在设计上对任何能访问到它的人都是一个远程代码执行面 —— 整套安全模型的存在就是为了控制*谁*能访问。（启动权限模式可配置，见下文。）近期加固（v0.9.0 + v0.9.5）封堵了那些常困扰自托管开发工具的浏览器驱动攻击路径。完整模型：[`docs/security-architecture.md`](docs/security-architecture.md)。**发现了漏洞？** 私下披露方式与已知限制清单见 [`SECURITY.md`](SECURITY.md)。
+Codeman 默认用 `--dangerously-skip-permissions` 启动会话，因此 Web UI 在设计上对任何能访问到它的人都是一个远程代码执行面 —— 整套安全模型的存在就是为了控制*谁*能访问。（启动权限模式可配置，见下文。）近期加固（v0.9.0 + v0.9.5）封堵了那些常困扰自托管开发工具的浏览器驱动攻击路径。完整模型：[`docs/security-architecture.md`](docs/security-architecture.md)。**发现了漏洞？** 私下披露方式与已知限制清单见 [`SECURITY.md`](.github/SECURITY.md)。
 
 ### 网络与访问
 

docs/versioning-policy.md

@@ -75,5 +75,5 @@ allowance. The commitments above take effect at `1.0.0`.
 ## See also
 
 - `CLAUDE.md` — the COM release workflow (changesets, version bump, deploy)
-- `SECURITY.md` — security reporting and the supported-version policy
+- `.github/SECURITY.md` — security reporting and the supported-version policy
 - `docs/security-architecture.md` — the full trust model