feat(ginit): 新增一键初始化本地 Git 仓库命令

`quicommit ginit`（别名 `gi`）离线完成仓库起步：用 git2 建库并确立初始分支、
写最简 README.md、按根目录标志文件装配 .gitignore、按 --add 添加远程，
`--profile` 可选套用已有 Git 配置。在已有仓库上重复执行只补齐缺失项：绝不覆盖
既有的 README.md/.gitignore、绝不改动已有 remote 的地址、不提供 --force、
不创建首个提交。边界取舍见 ADR 0006，命令命名见 ADR 0005。

实现落在新的 src/git/init.rs（9 个 git 层函数）与 src/commands/ginit.rs，
命令层不直接引用 git2，GitRepo 公开接口未改动，其余命令行为不变。
测试：src/git/init.rs 11 条单元测试、tests/ginit_tests.rs 18 条集成测试；
新增 35 个 ginit_* 消息覆盖 7 种语言。

另将 CONTEXT.md 与 docs/adr/ 纳入版本跟踪（.gitignore 放开 adr/ 与
CONTEXT.md 两条忽略规则）；RAODMAP.md 除 ginit 条目外还包含此前未提交的
规划条目更新。

docs/adr/0003-output-channels-and-message-prefixes.md

@@ -0,0 +1,7 @@
+# Output channels, message prefixes, and the decoration switch
+
+QuiCommit's user-facing output follows fixed conventions: stdout carries results and interactive content, stderr carries diagnostics; the hidden `credential` subcommand keeps stdout protocol-only (errors on stderr prefixed `[quicommit credential]`). Message text — `Messages` keys and inline command strings alike — never embeds emoji or status symbols; decoration prefixes (✓/✗/⚠/→, spinner frames) are applied only by the shared `utils` print helpers, so they can be toggled centrally. Decoration is configurable via `output.emoji` (bool, default on) with global `--emoji`/`--no-emoji` overrides (precedence: explicit flag > config > default); `--no-color`/`NO_COLOR` is highest priority and disables both color and decoration. When decorations are off, output is plain text with no severity labels — errors stay distinguishable via stderr and anyhow's `Error:` prefix. Emoji is not auto-disabled on non-tty (explicit control only), while color keeps `colored`'s existing tty auto-detection.
+
+**Considered Options**: emoji embedded in message text per language (rejected — decoration duplicated across 7 languages, half-on states when toggling, and two competing styles already coexisted in the codebase); text severity labels (`Warning:`/`Error:`) substituted when decorations are off (rejected — 7-language label burden for marginal value; stream separation already distinguishes errors); auto-disabling emoji on non-tty (rejected — emoji is a content-level choice, not a terminal capability, and script authors get explicit control via `--no-emoji`).
+
+**Consequences**: every future command author must route output through the helpers and keep message text decoration-free. Existing tests pinning English output stay valid because the default language is English. `--no-color` now also strips decorations — a behavior change from 0.6.x, where the flag was parsed but ignored (a review finding).