docs(code-runner): AGENTS.md 补充别名归一化与 bun 镜像说明

Code Runner API 层描述补充 normalize_lang 别名归一化机制:
- parse_fence_info 在 markdown 渲染期把别名(js→node, ts→bun 等)换成 canonical
- start_exec/start_exec_stream 在 LANGUAGES.get 前显式 normalize_lang

Runner images 段落补 yggdrasil-runner-bun,记录三个踩坑点:
- bun 不在 Alpine 3.18 仓库,用 bun.sh 脚本(自动选 musl 变体)
- bun 的 musl 二进制是 C++,需 libstdc++ + libgcc 运行时
- BUN_INSTALL 必须 export,否则 curl|bash 管道右侧读不到

AGENTS.md

@@ -181,14 +181,14 @@ src/infra/        — Docker execution layer + runner config (server-only); see
 Readers can execute fenced code blocks in isolated Docker containers; authors get a `/admin/runner` trial sandbox. Three-layer architecture, all Docker interaction gated behind `#[cfg(feature = "server")]`:
 
 - **Execution layer** (`src/infra/docker.rs`, server-only): `bollard` client over Unix socket (`DOCKER_CLIENT` LazyLock). `run_in_container` creates a read-only-rootfs container (tmpfs `/code`,`/tmp`,`/run`; cpu/memory/pids/ulimits cap; `cap_drop=ALL`; `no-new-privileges`; non-root `1000:1000`; `network_mode` none/bridge), injects source via stdin, waits with timeout, captures stdout/stderr (truncated to `output_bytes`), inspects OOM, force-removes via `ContainerGuard` Drop. `src/infra/runner_config.rs` (`RUNNER_CONFIG`) reads all `CODE_RUNNER_*` env vars; `clamp_limits` AND-merges request overrides × language `allow_network` × global switch.
-- **API layer** (`src/api/code_runner/`): shared `ExecRequest`/`ExecResult`/`ExecStatus`/`ExecTask` structs (compile on both targets); `progress.rs` = DashMap task registry + `gc_old_tasks`; `languages.rs` = `LANGUAGES` registry + `parse_fence_info`; `execute.rs` = `StartExec`/`GetExecResult` server functions (double rate-limit → whitelist → size check → enqueue → `tokio::spawn` + `RUNNER_SEMAPHORE` concurrency cap → clamp → run_in_container). System errors are sanitized to 「系统暂时不可用」 for anonymous callers; full errors in server logs only.
+- **API layer** (`src/api/code_runner/`): shared `ExecRequest`/`ExecResult`/`ExecStatus`/`ExecTask` structs (compile on both targets); `progress.rs` = DashMap task registry + `gc_old_tasks`; `languages.rs` = `LANGUAGES` registry + `parse_fence_info` + `normalize_lang` (alias normalization: `js`/`javascript`→`node`, `rs`→`rust`, `ts`/`typescript`→`bun` — done in `parse_fence_info` so `data-lang`/`ExecRequest.language`/`LANGUAGES.get` only ever see canonical keys `python`/`node`/`go`/`rust`/`bun`); `execute.rs` = `StartExec`/`GetExecResult` server functions (double rate-limit → whitelist → size check → enqueue → `tokio::spawn` + `RUNNER_SEMAPHORE` concurrency cap → clamp → run_in_container). `start_exec`/`start_exec_stream` call `normalize_lang(&req.language)` before `LANGUAGES.get` so aliases survive the wire. System errors are sanitized to 「系统暂时不可用」 for anonymous callers; full errors in server logs only.
 - **Markdown/render layer**: a fenced block ` ```python runnable {...overrides} ` renders to `<pre data-runnable="true" data-lang="python" data-overrides="..." data-source="...">` (sanitizer whitelists these 4 attrs on `<pre>`). `PostContent` (`src/components/post/post_content.rs`) splits `content_html` into `Html`/`Runnable` fragments so each runnable block renders as a real `<CodeRunner>` vdom element (no manual DOM mutation → no hydration conflict). `CodeRunner` component polls `GetExecResult` via WASM-friendly `sleep_ms`. Output is rendered into an xterm.js terminal instance (`src/xterm_bridge.rs` + `libs/xterm-terminal`, mirroring the codemirror bridge pattern) — stdout/stderr streamed via SSE, with full-buffer `writeAll` as a polling fallback.
 
 **Critical WASM-visibility rule**: `code_runner/execute.rs` is **not** cfg-gated (server functions must be visible to the client), but every server-only `use`/static inside it is individually `#[cfg(feature = "server")]`. The shared `use` of `ExecRequest`/`ExecTask` (used in signatures) stays ungated. `code_runner/languages.rs` and `code_runner/progress.rs` (pure server helpers) are wholly gated. Mirrors the `posts/` module convention.
 
 **Governor 0.8 caveat**: `Quota::per_day` does not exist; `CODE_EXEC_DAILY_LIMITER` uses `Quota::with_period(24h).allow_burst(daily)`. `RATE_LIMIT_CODE_EXEC_PER_SEC` must be an integer (governor's `per_second` takes `NonZeroU32`; decimals in `.env` fall back to the default 1).
 
-**Runner images** (`docker/`): `build-runners.sh` builds `yggdrasil-runner-base` → `yggdrasil-runner-python` → `yggdrasil-runner-node` → `yggdrasil-runner-go` → `yggdrasil-runner-rust`; tags must match `LANGUAGES` image fields. Python image symlinks `python`→`python3` to match `run_cmd`. Go image redirects `GOCACHE`/`GOTMPDIR`/`GOPATH` to `/tmp` (read-only rootfs makes `$HOME/.cache` unwritable). Rust image ships a `/usr/local/bin/run-rust.sh` wrapper because `rustc` compile + run is two steps and `docker.rs` injects `run_cmd` via `exec` — `exec A && B` would replace the shell and never reach `B`, so the two steps are encapsulated in the wrapper. `runner.toml` files are image self-descriptions only — runtime config is the Rust `LANGUAGES` registry + `CODE_RUNNER_*` env, not parsed from toml.
+**Runner images** (`docker/`): `build-runners.sh` builds `yggdrasil-runner-base` → `yggdrasil-runner-python` → `yggdrasil-runner-node` → `yggdrasil-runner-go` → `yggdrasil-runner-rust` → `yggdrasil-runner-bun`; tags must match `LANGUAGES` image fields. Python image symlinks `python`→`python3` to match `run_cmd`. Go image redirects `GOCACHE`/`GOTMPDIR`/`GOPATH` to `/tmp` (read-only rootfs makes `$HOME/.cache` unwritable). Rust image ships a `/usr/local/bin/run-rust.sh` wrapper because `rustc` compile + run is two steps and `docker.rs` injects `run_cmd` via `exec` — `exec A && B` would replace the shell and never reach `B`, so the two steps are encapsulated in the wrapper. Bun image uses the official `bun.sh/install` script (bun isn't in Alpine 3.18 repos; the script auto-detects `/etc/alpine-release` and picks the musl variant) and must `apk add libstdc++ libgcc` — bun's musl binary is C++ and needs the C++ runtime that musl libc alone doesn't provide; `BUN_INSTALL=/opt/bun` is `export`-ed so the pipe `curl | bash` reads it on both sides (a bare `VAR=x curl | bash` only sets it for curl, making bash fall back to `$HOME/.bun`). `runner.toml` files are image self-descriptions only — runtime config is the Rust `LANGUAGES` registry + `CODE_RUNNER_*` env, not parsed from toml.
 
 ## Frontend Lib Subprojects