fix(m163): push tag 默认建稳定版（发布标记语义 + 0.2.3 bump）

发布标记：`release.yml` 的 dispatch `prerelease` 默认值 true → false；`release-publish.yml`
的 create 路径不再塞 `--prerelease`（空串 = push tag ⇒ 稳定版），edit 路径行为不变（空串不碰
标记）。三种触发各创建什么改由 `packaging/release_marker.py` 一张表定义，流水线
`--emit-bash` 出来两个数组直接用，自己不再写 case——v0.2.2 至今 `releases/latest` 404 的根因
就是「push 默认 prerelease」这层叠上「dispatch 默认 true」。

守门：新增 `packaging/check_release_semantics.py`（CI 在 `.github/workflows/release-guard.yml`，
guards.yml 已 398 行不能再挂 job）：①标记表逐条对（push tag 的 create 不含 --prerelease）；
②把 `--emit-bash` 真灌进 bash 读回两个数组；③publish 的可执行内容里没有 --prerelease 字面量、
必须调用 emit-bash、两个数组各喂 create/edit；④release.yml 的 dispatch 默认值 == false（读
YAML 结构）。`--self-mutation` 注入三项真实回归（默认值改回 true / 塞回字面量 / 表里 push
改成预发布），断言每项都红、基线绿。

版本：0.2.2 → 0.2.3（workspace `[workspace.package]` + 五处 path 依赖 pin + Cargo.lock）。

文档：README 中英两版版本行改 0.2.3，并把本阶段能力补进现有章节（Modrinth 匿名在线内容源、
自更新与稳定通道、整合包导入逐文件决策、实例级启动参数），删掉「没有自动更新通道」「导入只有
两份全局策略」两条过期说法；`release-notes.md` 写 0.2.3 的真实更新摘要（保留 {{VERSION}} /
{{SUMS}}）；`packaging/README.md` 与 `docs/build-and-ci.md` 里「push 默认仍 prerelease」的旧口径
全部改掉。

packaging/release-notes.md

@@ -4,6 +4,26 @@ Rust-native **single-file** Minecraft launcher: iced 0.14 + Material 3 Expressiv
 (chat / setting edits / crash diagnosis) and an MCP server other agent tools can attach to.
 No WebView, no bundled runtime, no JRE download needed to start the launcher itself.
 
+## What's new in {{VERSION}}
+
+- **{{VERSION}} is the first release published as a stable release.** GitHub only points
+  `releases/latest` at the newest **non-prerelease** release, so `0.2.2` — kept as a historical
+  pre-release, untouched — never appeared there. A pushed tag now creates a stable release by default;
+  a pre-release has to be asked for explicitly (`workflow_dispatch` with `prerelease=true`).
+- **Self-update works end to end.** `ull update check` / `ull update apply` and the settings panel's
+  Update group share one core (`crates/core/src/update/`): manifest, version and channel admission,
+  length + SHA256 verification, and an atomic rename-based swap that rolls back on failure. Only the
+  stable channel is published today.
+- **Online content library (Modrinth, anonymous).** Search, project details and version lists come from
+  Modrinth's v2 API with facets derived from the target instance, and a known hash completes a remote
+  entry. Being offline is reported as "not connected", never as "no matching content".
+- **Per-file decisions when importing a modpack.** The pre-import scan lists every conflicting file in
+  pages of 40, and you choose keep-all, overwrite-all, or per item; files that do not conflict are
+  never rewritten, and the report names every conflict afterwards.
+- **Per-instance launch arguments.** JVM arguments, game arguments, memory, the Java executable and the
+  graphics backend (`default` / `opengl` / `vulkan`) are set per instance, each field falling back on
+  its own to the global setting and then the factory default. The CLI reads the same resolved values.
+
 ## Downloads
 
 Asset names are `<name>_<version>_<platform>_<arch>`, underscore separated — the rule
@@ -44,6 +64,14 @@ Each published slot also ships the command line as its own small bare asset,
 `config`, `java` and `agent`, and links no graphics library at all. The GUI binary accepts the same set
 before it ever opens a window, so a desktop machine does not need `ull`.
 
+## Updating
+
+The launcher reads `releases/latest/download/manifest.json` on startup (switchable: `update.auto_check`)
+and shows four distinct outcomes: up to date, an update is available, a newer version exists but ships no
+artifact for this platform, or the check itself failed. `ull update check` prints the same verdict, and
+`ull update apply` downloads, verifies SHA256 and swaps the binary atomically, rolling back if the swap
+fails. Nothing installs without you asking for it.
+
 ## Support matrix
 
 Published = shipped as a download of **this** release, listed in `SHA256SUMS.txt`.